Study of Automation of HVAC System and Component Improvements for Improved Performance

8/9/2019 Study of Automation of HVAC System and Component Improvements for Improved Performance

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Study of Automation of HVAC System and Component

Improvements for Improved Performance

A Graduate Project Report submitted to Manipal Univeristy in partial fulfilment

of the requirement for the award of the degree of

Bachelor of Engineering

In

Mechanical Engineering/Industrial and Production Engineering

by

Nikhil Mohan

Under the guidance of

Dr. U. A. Kini

Department of Mechanical &Manufacturing Engineering

MANIPAL INSTITUTE OF TECHNOLOGY

DEPARTMENT TOF MECHANICAL AND MANUFACTURING ENGINEERING

MANIPAL INSTIITUTE OF TECHNOLOGY

(A constituent Institute of MANIPAL UNIVERSITY)

MANIPAL 576104, KARNATAKA, INDIA

January 2014


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DEPARTMENT TOF MECHANICAL AND MANUFACTURING ENGINEERING

MANIPAL INSTIITUTE OF TECHNOLOGY

(A constituent Institute of MANIPAL UNIVERSITY)

MANIPAL 576104, KARNATAKA, INDIA

January 2014

CERTIFICATE

This is to certify that the project titled Study of Automation of HVAC System and

Component Improvements for Improved Performanceis a record of the bonafide work

done by Nikhil Mohan (090909094) submitted in partial fulfilment of the requirement for

the award of the degree of Bachelor of Engineering in Mechanical Engineering of

Manipal Institute of Technology, Manipal, Karnatak (a constituent of Maipal University)

during the year 2013-2014

Dr. U Achyuth Kini

Project guide

Dr Divakar Shetty

Head Of Department


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ACKNOWLEDGMENTS

I would like to express my deepest appreciation to all those who provided me the possibility to

complete this report. A special gratitude I give to my project guide, Dr. U A Kini, whose

guidance and encouragement have helped me coordinate and complete this project.

Furthermore I would also like to thank the staff of the Mechanical Department, without whose

help, guidance and permission to use the instruments this project could not be completed. I

would like to thank every professor who helped provide guidance and aid to this project.


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ABSTRACT

In todays ever environmentally conscious world energy conservation has become a very

important issue. In smaller house holds the air-conditioner uses up a major portion of the total

monthly energy consumed. The same way in larger structures and spaces, a large amount of

energy is consumed by Heating Ventilation and Air Conditioning units. These large systems

are often put into place to handle large loads for large numbers of people and maintain a space

at a habitable condition. However a lot these system do not have optimised capacity for

handling lower loads and often consume extra energy when faced with these low loads.

These systems however also, when considered in a work environment, have patterns and

characteristics of usage. With the use of these patterns of usage and minimum load instructions

the systems energy consumption can be optimised to conserve energy and thereby also cost.

LIST OF NOTATIONS AND ABBREVIATIONS

HVAC Heating Ventilation and Air Conditioning

BMS Building Management System

AHU Air Handling Unit

RF-id Radio Frequency Identification


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LIST OF FIGURES

Figure Number Title of Figure Page Number

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

Chiller Plant

Plant Layout

Cooling tower

Cooling Tower Layout

Air Handling Unit

AHU layout Library

AHU layout IC + NLH

No. of people/room temperature 1

AHU cut-off

No. of people/room temperature 2

AHU with cooling

Surface Temperature

Library Main Hall

TBS Temperature/no. of people

2ndFloor Library Heat zones

Innovation centre heat zones

Temperatures + No. of People NLH

11

12

13

13

14

15

16

24

24

25

25

27

28

29

29

30

31


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LIST OF TABLES

Figure Number Title of Figure Page Number

1

2

3

4

5

6

7

8

9

10

11

12

13

The Library Time/room temp/no of people 1

The Library Time/room temp/no of people 2

Time/Cooling Tower

Time/Inner/Outer/Glass Temp

Main hall time/no of people/vent temp/ext temp

NLH 203

NLH 205

NLH 403

NLH 404

Computer Lab 3rdFloor IC

4th Floor Public Area IC

4th Floor 04 Classroom IC

Time/Inlet/Outlet

24

25

26

27

28

31

32

32

33

34

34

34

35


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CONTENTS

ACKNOWLEDGEMENTS

ABSTRACT

LIST OF NOTATIONS AND ABBREVIATIONS

LIST OF FIGURES

LIST OF TABLES

3

4

4

5

6

Chapter 1

1.11.2

INTRODUCTION

Problem StatementIdeology of Solution

Chapter 2

2.1

2.2

2.3

2.4

LITERATURE REVIEW

Central HVAC Plant

AHU Systems

Design Parameters

Energy Consumption

Chapter 33.1

3.2

OBJECTIVES AND METHODOLOGYObjectives

Methodology

Chapter 4

4.1

4.2

4.3

RESULT AND ANALYSIS

Design Parameters

Current System

Trends and Patterns

Chapter 5

5.1

5.2

5.3

CONCLUSIONS AND SCOPE OF FUTURE WORK

Inferences

Improvements and Future Design Considerations

Scope for Future Work

8

89

11

11

14

16

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1818

18

20

20

23

24

36

36

38

41

REFERENCES 42


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1. Introduction

1.1 Problem Statement

Air conditioning is the process of treating air so as to control simultaneously its temperature,

humidity, purity, distribution, air movement, and pressure to meet the requirements of the

conditioned space. In a buildings, it provides conditions to people so that they can live and

work in comfort, safely, and efficiently. In common perspective, air conditioning is generally

associated to cooling and dehumidification during the summer and monsoon seasons when heat

is extracted from the space.

For larger spaces, HVAC units or plants are set up to manage the cooling and dehumidification

of spaces occupied by a large number of people. These spaces can be either places of low

activity like houses, hotel rooms, and other residential areas, or hubs of activity like offices,

work places, gyms, libraries, etc. These systems manage and handle the air conditioning for

sustained periods of time and function under all environmental conditions.

These systems are first designed on specific parameters around which they would be

functioning. These parameters and factors that are used for the design of such systems are

usually very linear in their approach and are based on environmental factors, required condition

of the air, tonnage of air to be cooled, humidity, etc. These factors are set into place and used

to define the design parameters for the system. A system is then selected to meet these

requirements and installed with recommendations from manufacturers. Even though these

systems account for load requirements and have redundancies in case of excessive load, they

do not have any systems in place for reduction in consumption of energy at times when the

load is low. They have cut-off triggers and actuators for system standby till the load the

surroundings being conditioned reach an upper threshold at which the system will resume

working.

This type of system working is very linear and does not account for variation in loads by set

patterns of weather, day time, number of people, air swapping, etc, and hence cannot be

completely efficient in its energy use. This poses a problem as a system that could hence be

saving energy at lower load times continues to run at near full capacity to provide for a fraction

of the load. In light of that even Schneider Electric released a problem statement for devising


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an automation system of HVAC systems of large office buildings to optimise their

performance. This is also a major factor in international environment friendly protocols for

building construction and maintenance practices. In terms of energy efficiency, older systems

fall behind compared to more recent ones as concerns for these factors, environmental or

otherwise were not used to design them.

Also these systems have certain components and subsystems that can be optimised to increase

their performance. These factors sometimes go overlooked and can be a source of

improvement, if only minor, of the performance of these systems. The components that come

under the purviews of improvements are often ducts, their placements, the distribution system,

heat exchangers, cooling towers, etc. Placement of ducts, leakages, exposure to heat, insulation,

draft types in cooling tower, water loss, etc all can reduce the actual energy transfer and

especially if the mass of air or water has to travel larger distances to the place where the cooling

must be provided the energy loss increases.

1.2 Ideology of Solution

Here, in this study, the Library at MIT Manipal has been chosen as one such system. The age

of the system is significant compared to recent systems and has loads that vary to a great degreeover the course of a day and over the course of the week. The climatic conditions around the

system also have somewhat regular patterns. This system also has many older components, that

though have been serviced could possibly have scope for improvement. This system provides

cooling and working to a series of buildings that significantly represent an office space i.e. a

large number of people enter and leave these spaces and the trend for their presence can be

tracked for a long period of time. These buildings face regular and patterned solar exposure

and hence have measurable and patterned solar gain.

One final factor that plays an important role in the proper and efficient functioning of any

system is maintenance and care. If the system has suffered decay, corrosion, and

eutrophication, which HVAC units are prone to, they will suffer energy and in turn efficiency

losses. Broken components like thermostats, thermal sensors, actuators, etc. will cause also

hinder the functioning of the system as the values and inputs required for cut-off at threshold

and consume energy unnecessarily.


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Large HVAC systems also have a centralised control system called a BMS or a building

management system that measures checks, acts as a centre for controlling the system, virtual

switchboard for functions in the system and a feed for all data from the different sensors in the

system. These systems require constant checks and monitoring and need an operator at all times

to manually turn off and on the systems that need to run and that should be turned off. An

automation system would allow the BMS to work on a learning algorithm that understands and

matches patterns to those already input by the designers based on the building requirements.

This would allow the system to save energy by automatically and efficiently regulating the

required parameters to meet the desired load. The system itself would have full manual control

over the working of the unit in case required.

This project is a study of all these factors coming together to make HAVC systems more

efficient using the case of a preinstalled, the HVAC unit for the academic blocks of MIT, to

study where the system has scope for improvement. The study hopes to reveal trends and

patterns for peak loads and how to direct the system to intuitively learn maximum load timings

and variations in order to improve performance.


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2. Working of the Present System / Literature Review

2.1 Central HVAC Plant

The current HVAC plant installed is put in place behind the library and comprises of 2 screw

type and one centrifugal chillers. These are connected to 4 cooling tower, out of which one is

a redundant failsafe. This plant cools 3 buildings out of which one is currently under study by

this project.

2.1.1 Chiller System

The current chiller system employed utilises 3 discrete chiller plants, two screw type

compression chillers and one centrifugal type compression chiller. All these systems are

installed and were designed by Carrier Corporation. As any chiller system, they have 4 major

components, the compressor, the condenser, the throttle valve and the chiller.

1ChillerPlant

The compressors in these systems define the capacity and extent of load handled. The screw

type chillers take less load, while the centrifugal chiller takes more load.

Each chiller however has the same set of inlets and outlets.

1. Water returning to the chiller from AHUs in the buildings

2. Water going from the chiller to the AHUs in the buildings

3.

Water going to the cooling towers from the condenser

4. Water returning from the cooling towers to the condenser

These form 2 separate cycles of water that acts as a working fluid for transfer of heat. One

that transfers cold water to the AHUs for cooling the building spaces. A 3 pump system is


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used to ensure uniform distribution to each of the required spaces, i.e. the NLH, IC, and

Library. The same is applied with 4 pumps for the return of used water to the chillers. This

water is usually in a temperature range of 7.5 to 13 degrees Celsius and is cold enough to

allow the temperature from the vents of the rooms and halls to be 16 degrees Celsius which is

usually the lowest set point for cooling of any HVAC system. The temperature of the water

going out depends also on the temperature of the water coming into the plant. If the load on

the plant is extremely high then the water entering the chiller is too warm to be cooled

sufficiently enough to meet the requirements of the temperature set point of the water leaving

the chiller. The load on the plant reduces both as the area being cooled loses heat and the

actual sources of heat i.e. people and solar exposure reduce. At this point the chiller water

cycle comes back to an equilibrium of set temperature and the plant comes back to normal

load functioning.

At other times the plants must be manually turned off to prevent work from being done for an

almost no load requirement environment in the areas being cooled. At this point the room or

hall can become too cold even after cut-off as the of cold air remains to the AHUs. Even if

the AHUs cut-off cooling, with no heat loss to surroundings the room grows colder and often

uncomfortable. Thus chiller plant energy consumption is wasted in maintaining an area

cooled without requirements.

PlantLayout


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2.1.2 Cooling Towers

The cooling towers employed by this plant to remove heat from the gas in the condenser are an

upward induced draft type. This means that a powerful fan is used to suck air from the bottom

of these towers.

The water falls from the top of the tower and

is forced to interact with upward flowing air.

This interaction causes the water evaporate

and hence cool the surrounding falling water

by a few degrees. Though this method is

effective, there is a certain amount of loss of

water due to vaporisation. This means that

water must constantly be replenished into the

system. The water entering the cooling tower

is usually at 36 to 38 degrees Celsius.

Coolingtower

Cooling

tower

layout

The water that exits the cooling tower can be between 31 to 27 degrees Celsius. This allows

one to judge the load on the plant as the higher the temperature of water leaving the cooling

tower, the higher the load on the plant. A lower temperature of water leaving the cooling tower


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also means that the effectiveness of the condenser increases and hence can directly improve

the performance of the system. Though these towers are designed based on given

environmental and load parameters the effectiveness can vary and still be increased as

conditions and loads vary. Also the condition of the tower itself can mandate the effectiveness.

If the tower has algae or corrosion effecting the inner lining the effectiveness of the system is

reduced and can also cause damage to the piping and cooling of the entire system as a whole.

Thus this must be taken care of with great importance.

The piping of this system also plays a major role in how efficiently this system works as if the

piping and layout is not placed correctly the heat loss and gain to the surroundings can increase

and hence decrease the efficiency of the system as a whole. The piping if too long and exposed

to the sun for long periods of time, even after being insulated, can absorb heat and reduce the

effectiveness.

2.2 Air Handling Unit

Airhandlingunit

The air handling unit utilises water that comes from the chiller to cool the air for a certain area.

Usually each segregated area has an AHU allotted to it for cooling and maintaining air quality.

AHUs not only provide cooling but also maintain humidity, maintain Carbon Dioxide and

Carbon Monoxide levels in parts per million so as to not allow an area to become toxic.


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These systems consist of a centrifugal blower that directs the air and blows it into the ducts and

into vents. This starts a draft and current in the room to provide cooling. The fans usually suck

in air from one inlet that faces a mesh where water flows as a cooling medium. The water flows

through the mesh and cools it. Once the water supply to the AHU is cut-off the air passes

through an un-cooled mesh and doesnt get cooled itself enough to cool the surroundings and

thus the systems cut-off is controlled by thermostats that turn-off and on the AHU cold water

supply. If the amount and mass flow rate of cold water onto the AHU mesh is controlled by the

use of an actuator or digitally operated valve, the required amount of cooling can be provided

in smaller burst when need rather than having the entire system be active to provide cooling in

times of low load.

The following diagrams show the Layout for the AHU in the Library, the Innovation centreand the New lecture Halls. It shows the segregation and direction of usage of these AHUs and

how theyre linked to the central system.

AHUlayoutLibrary


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2AHUlayoutIC+NLH

As the AHUs act as distributers of the cold air, they are the central source of consumption of

the load to the chiller plant and thus directly impact the final and total load on the system as a

whole. Knowing this design parameters for AHUs can be altered and guided to allow for a

maximum efficiency of load distribution.

2.3 Design Parameters

Usually the design parameters for an HVAC system based on load are as follows:

1. Volume Tonnage: The volume of air to be cooled or the size of the area to be

conditioned.

2.

Humidity Regulation: Based on the humidity of the ambient air, the humidity in the

enclosed space can be set and regulated to maintain a comfortable environment.

3.

Heat Sources: The sources of heat around the area to be cooled, such as the heat from

the lighting, from people, from walls, etc. must be managed efficiently.

4. AHU Fan power: To ensure a continuous draft for the flow of air to be constant and

directed correctly for optimum comfort.

5. Sensor placement: The placement of sensors in the system can and often dictate how

the reading and how the system responds to the information.


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6. Air Change rates: This is used to ensure that stale air does not get cycled over and over

and that fresh air gets swapped into the system so the CO2levels do not rise.

7. Mass Flow rates: The amount of water required to be flowing in both the condenser and

the chiller cycles to ensure optimum transfer and flooding of pipes.

These parameters put together with many smaller others are used to design the initial scope and

usage of the system. As mentioned earlier these parameters are fixed when the design is drawn

up and are designed for maximum load centric performance. They can be optimised to allow

the system to conserve energy.

2.4 Energy Consumption

The energy consumed by the system is directly linked to the cost associated with running the

system. A system running in its peak and optimum condition will have a noticeably lower

running cost than one that is inefficient. The current system has an energy meter to track its

energy usage per day and is logged for everyday to check for tracking its usage and energy

requirements.

A significant portion of the energy consumed by these systems is by the central chiller plants.

Hence if the total energy in the system is to be reduced the total load on the plants must also

be directly be reduced. The following table shows the average daily consumption of energy of

the system on the given days of the week.


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a. Piping

b. Ducts

c. Cooling tower

d.

Pumps

5. Check components for scope of better maintenance. Check for corrosion, leakage,

breaking etc.


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4.1.2 Solar Exposure and Time of Day

Depending on the buildings location it can have varying degrees of exposure to sunlight

during the day. A building in the northern hemisphere above the Tropic of Cancer, if aligned

along the east-west direction will get the brunt of the sunlight from sunrise to sunset. The

same way, a building aligned along the north-south direction on any latitude will face

sunlight on one side in the morning and one side in the evening.

A building surrounded by other buildings is greatly protected from the direct radiation of the

sun. This allows the building to retain a large amount of heat and not lose energy to heat from

the sun.

The alignment of the building also dictates how the different heat zones will form across thebuilding. These heat zones, if tackled properly- can significantly reduce the amount of energy

lost to solar exposure.

Heat gain from solar energy and external air is one of the most significant causes of increased

energy consumption by the HVAC System.

Directed cooling at these heat zones created by solar exposure can greatly improve the

performance of a system as the heat generated by the walls and windows is directly and

cleanly absorbed; thereby helping the system maintain a comfortable temperature in space.

4.1.3 Climatic Variations

Weather and climate directly control the external conditions that the system must overcome

to maintain the specific conditions within the space. The climate of any given place follows a

yearly pattern that does not vary significantly. These conditions can therefore be mapped out

and a trend can be generated to allow the system to intuitively understand the needs of the

space being conditioned.

Though the weather changes daily it still follows the general trend of the climate of the

location. Since weather directly influences the conditions the plant must overcome, it

becomes an important factor to consider in making an intuitive system.

Climatic data over the last few years of any location can be used as a reference to map its

trend and teach the system the variations in load over the months. For example, a system can


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be instructed to understand that during summer, due to high external load, a more lax

approach to energy conservation can be put in place. However in months of rain and winter,

the system can learn that since climatic conditions outside are closer to the ones needed to be

maintained within the space, a stricter regime of energy conservation must be followed.

This also allows the concept of free cooling to aid the system in reducing its energy

consumption. Free cooling is when the air outside the space to be cooled is very close to the

temperature to be maintained within. This allows the system to swap fresh air directly from

the surroundings with a small level of cooling and maintaining humidity to condition the

space to a comfortable level. Free cooling allows the system to not use the chilled water from

the plant and thereby save energy.

4.1.4 Insulation and Reflective Shielding

Materials that are used for the faade of the building dictate how much heat the building will

gain. Buildings made of brick and concrete have a greater factor of insulation to the heat as

compared to buildings with the faade of glass.

For walls the insulation materials can be added directly in the mortar and thereby increase the

capacity of insulation. Recently, new materials such as astrofiber, which are extremely light

and highly insulated, can be mixed in the mortar and bricks. Even using waste plastic directly

in the mortar makes for cost effective insulation for buildings.

Since most buildings today utilize artificial lighting indoors the need for natural light has

reduced significantly. Therefore, reflective surfaces can be added to glass, which reduce the

infrared radiation entering the building. These reflective surfaces therefore directly reduce the

amount of heat gained by the buildings through the glass.

4.1.5 Thermal zoning

In any active space, there are always zones or areas that generate the most heat and hence are

centers for the maximum load to the system. It becomes very important to identify these

zones and thereby provide effective cooling to reduce the overall effect they have on the

system.


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The hubs of high activity, large computing centres, windows and walls exposed to sunlight,

cooking spaces and areas next to doors can be easily be identified as high heat zones.

Pantries, places of high activity, computer zones can usually be effectively cooled by

providing high output diffusers or vents that provide high levels of circulation. This cools the

area, thereby significantly reducing the heat it spreads to the entire system.

Walls, windows and cooking areas should preferably have vents over them to suction out the

hot air, so as to effectively reduce the heat immediately from the system. This allows cool air

to be circulated into the region faster and the hot air to be removed and thereby maintaining

the conditions required for the area.

As a general principle, doors that open out to the outside environment usually have a high

power blower generating an air wall that prevents hot air from the outside from mixing with

the cool air inside.

4.2 Current System

The current system is designed with the basic design parameters in mind and has been

designed to handle a redundantly high load if the need arises. However this system itself does

not prepare for low loads and has issues with circulation. This entails that the system isdirectly consuming large amounts of energy that can thus be conserved.

Most systems in place in buildings, the direct set of design parameters, ensures cooling and

maintaining a specific condition in the given space however it does not always aim at energy

conservation.

The current systems are not smart and often need direct or complete supervision to run

efficiently and run without a hitch. This increases the effective cost of the system and also

leaves room for negligence in monitoring the system. Though a BMS manages a system

fairly well it only regulates basic supply and demand parameters for the system and does not

monitor the actual load on the system.


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Time Room temp No. of people

09:00 AM 25.3 8

09:30 AM 25.3 48

10:00 AM 25.0 60

10:30 AM 24.5 62

11:00 AM 25.0 94

11:30 AM 24.2 80

12:00 PM 24.9 112

12:30 PM 24.8 118

01:00 PM 24.2 8401:30 PM 24.5 90

02:00 PM 24.9 100

02:30 PM 25.2 98

03:00 PM 24.7 100

03:30 PM 24.8 109

04:00 PM 24.3 82

04:30 PM 23.6 85

05:00 PM 23.5 89

05:30 PM 23.6 91

06:00 PM 24.4 93

06:30 PM 24.9 110

07:00 PM 24.7 95

07:30 PM 24.9 98

08:00 PM 24.7 80

08:30 PM 24.3 80

09:00 PM 24.1 32

09:30 PM 23.8 30

10:00 PM 23.3 22

10:30 PM 23.1 11

11:00 PM 22.5 8

24.36 74.34

15

15.5

16

16.5

17

17.5

18

18.5

19

19.5

09:00AM

10:00AM

11:00AM

12:00PM

01:00PM

02:00PM

03:00PM

04:00PM

05:00PM

06:00PM

07:00PM

08:00PM

09:00PM

10:00PM

11:00PM

AHUwithCooling

Airtempfromventlefton

09:00AM

10:00AM

11:00AM

12:00PM

01:00PM

02:00PM

03:00PM

04:00PM

05:00PM

06:00PM

07:00PM

08:00PM

09:00PM

10:00PM

11:00PM

Room

Temperature

2

Roomtemp

0

20

40

60

80

100

120

140

09:00AM

10:00AM

11:00AM

12:00PM

01:00PM

02:00PM

03:00PM

04:00PM

05:00PM

06:00PM

07:00PM

08:00PM

09:00PM

10:00PM

11:00PM

No.ofPeople

No.ofPeople


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The above data represents measurements from a day when the air conditioning in the hall was

active throughout the day and hence can be seen that the room temperature falls where the

number of people in the hall reduce. The same way when the AHU is cut-off the temperature

rises in the hall and makes it uncomfortable. The thermostat setting for the hall is 24degrees

Celsius and thus can be seen to vary around it.

At the same time the cooling tower water temperatures were checked to map load on the

system and corresponded with the load given by the number of people and the heat the

building faade received during the day.

Time Cooling Tower Out

09:00 AM 29.35

10:00 AM 30.5

11:00 AM 29.7

12:00 PM 30.5

01:00 PM 30.2

02:00 PM 30.8

03:00 PM 30.9

04:00 PM 31.1

05:00 PM 30.8

06:00 PM 29.4

07:00 PM 29.35

08:00 PM 31.9

09:00 PM 28.1

10:00 PM 27.9

11:00 PM 27.5

The AHU cut-off functioning blower air temperature is approximately 19 degrees Celsius and

can be seen in the above graphs. This shows and explains the marked increase in the room

temperature as the heat from the walls and the people could not be compensated enough to

maintain the room at a comfortable temperature. Increasing the performance of the system is

a major factor but human comfort cannot be ignored. Thus the automation system would


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balance the needs of both together and essentially allow the system to be cost effective and

useful.

The following data shows glass temperature and exposure to the hall to heat from the glass.

Time Inner outer glass temperature

09:00 AM 27.1 30.1 28.28571429

09:30 AM 27.2 34.9 28.6

10:00 AM 26.88 36 28.81428571

10:30 AM 26.7 36.6 29.48571429

11:00 AM 27.11 36.2 29.9

11:30 AM 27.3 36.4 30.1

12:00 PM 27.3 36 30.2

12:30 PM 27.5 34.6 29.8

01:00 PM 26.8 35.2 28.7

01:30 PM 27.4 34.4 29.5

02:00 PM 27.3 34.5 30

02:30 PM 27.2 34.3 30

03:00 PM 27.3 34.3 29.5

03:30 PM 27.4 34 29.1

04:00 PM 27.2 34 29

04:30 PM 27.4 33.2 28.2

05:00 PM 27.3 32.8 28

05:30 PM 27.3 31.6 28.3

06:00 PM 27.4 31.6 27.2

06:30 PM 28.4 31.6 28.6

07:00 PM 28 30.9 28.2

07:30 PM 28 30.3 2808:00 PM 27.8 30.3 27.8

08:30 PM 27.2 30.3 27.3

09:00 PM 27.3 29.5 27

09:30 PM 26.9 29.2 27.5

10:00 PM 26.6 28.8 27.1

10:30 PM 26.4 28.4 26.98

11:00 PM 26.1 28 26.86

27.23413793 32.68965517 28.55261084

20222426283032343638

09:00AM

09:30AM

10:00AM

10:30AM

11:00AM

11:30AM

12:00PM

12:30PM

01:00PM

01:30PM

02:00PM

02:30PM

03:00PM

03:30PM

04:00PM

04:30PM

05:00PM

05:30PM

06:00PM

06:30PM

07:00PM

07:30PM

08:00PM

08:30PM

09:00PM

09:30PM

10:00PM

10:30PM

11:00PM

SurfaceTemperature

InnerWall OuterWall WindowGlass


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The heat given off by the lighting in the library hall was also considerable as the grill holding

it showed a temperature of nearly 42degrees in an air condition environment. These fixtures

were also active throughout the day and hence contribute to the heat gained by the system.

However, during day time, in the presence of sufficient natural light the system would lose

less energy to these fixtures. If however these fixtures must be kept active, tinting of the

windows would serve as an alternative to reduce heat loss from the glass.

The Following data represents the Main hall of the Library.

Time Room Temp No. of People Vent Temp External Temp

09:00 AM 24 16 17.2 27.8

10:00 AM 23.8 22 16.7 33.8

11:00 AM 23.9 21 17 34

12:00 PM 24.1 32 16.8 34.5

01:00 PM 24.2 35 17.2 35

02:00 PM 23.9 28 17.5 34.5

03:00 PM 23.9 27 16.9 34

04:00 PM 24 25 16.6 32.7

05:00 PM 23.8 30 16.9 30.5

06:00 PM 23.7 40 17 30

06:30 PM 23.7 34 17 27.9

07:00 PM 23.6 5 17 27.5

23.88333333 26.25 17.16363636 31.85

The above data shows the how since the hall is significantly isolated and does not have a

very large number of people and the variation in the number of people does swing greatly

LibraryMainHall


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over the day the hall temperature does not vary too much. The hall however does get colder

as the lower levels do not have complete and proper circulation. The temperature therefore

continues to fall and the thermostat does not cut off appropriately and keeps consuming

energy.

In a similar way one of the larger more actively used halls has the following trend.

The black line represents the number of people, and the blue the room temperature. The trend

still has a similar pattern where it follows the load that trails behind the number of people in

the room. As the people in the room fall, as expected, the room temperature falls. It also

happens at the end of the day when the heat from the air is reduced.

The following diagram represents the zones for heating as noticed in the library on the second

floor where the GSH and the TBS are located.

2nd

floor

heat

zones

TBSTem erature no.of eo le


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These halls also have artificial lighting that remains on throughout the day and thus have no

special need of natural light. The light not only act as a source of heat themselves with the

mesh covering them reaching temperatures of 54oC and acting as significant sources of heat.

Also this makes clear windows a little redundant and therefore one or the other can be done

away during the day, i.e. either the lights be turned off and natural light be allowed to

illuminate the room or use reflective films on the glass to reduce heat transfer and use

artificial light in the hall.

4.3.2 New Lecture Hall and Innovation Centre

The central plant provides cooling to 2 other buildings, i.e. the New lecture halls and the

Innovation centre. The following diagram shows the heat zones in the Innovation centre.

3Innovation

centre

heat

zones

These zones shift during the day and time of day. The faade receives a significant amount of

heat from the morning sun and heats the building to a temperature near almost 27.2 27.6

degrees during the morning. The heat persists as there are no AHUs dedicated to the entire

area. The dround floor is kept cool by a single AHU and due to natural convection remains

that way. This area is a significant source of load.

The innovation center however in terms of human load has significantly lower loads than the

NLH. The NLH as a host to classes during the period of the day has a populous load of near

750-850 people every day. The load of people entering these classes does not vary

significantly from a norm as the time tables of most classes are set in advance and can thus be

used to generate a pattern for the usage of the halls. The halls themselves have a tendency,

however, to get cold over a period of time as again the circulation of air across them is not


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NLH 205

TimeRoom

TemperatureNumber of

PeopleGlass Temperature

(with Curtain)Glass Temperature(without Curtain)

Air fromvent

08:00:00 23.8 62 25.7 26.8 17.1

09:00:00 23.4 66 25.6 27 17.2

10:00:00 23.1 66 26 27.2 17.1

10:15:00 22.9 45 26.1 27.3 17

10:30:00 23.2 61 26.1 27.3 17

11:30:00 22.8 61 25.8 27.1 16.9

12:30:00 22.6 63 26 27.4 17.2

12:45:00 22.3 3 26.2 27.5 17.1

13:00:00 21.8 0 26.3 27.9 17.1

14:00:00 21.7 0 27.5 28.3 16.9

15:00:00 21.9 0 28.4 30.1 17

15:15:00 21.9 0 28.5 30.2 17.1

15:30:00 22 0 28.5 30.2 17.2

16:30:00 21.9 0 30.1 32.3 17.1

17:30:00 21.6 0 30.9 34 16.9

18:00:00 22.3 17 29.9 33.8 17.3

19:00:00 21.9 16 28.6 32.6 17.1

20:00:00 21.8 19 27.7 31.3 16.9

NLH 403

TimeRoom

TemperatureNumber of

PeopleGlass Temperature

(with Curtains)Glass Temperature(without curtains)

Air fromvent

08:00:00 24 59 29.3 35.4 16.9

09:00:00 23.7 62 34.5 42 17.1

10:00:00 23.4 62 34.4 42 17.2

10:15:00 23.2 23 34.3 42 17.2

10:30:00 23.8 61 34.7 42.1 17.2

11:30:00 23.7 61 34.9 42.2 17.1

12:30:00 23.5 62 34.6 41.9 17

12:45:00 23 4 34.6 41.8 1713:00:00 25.7 58 34.4 41.6 17

14:00:00 24.2 64 33.6 39.9 16.8

15:00:00 23.9 64 32.7 37.6 16.9

15:15:00 23.5 39 32.6 37.6 17

15:30:00 24.1 63 32.6 37.4 17

16:30:00 23.7 63 31.3 35.1 17.2

17:30:00 23.2 62 30.6 33.9 16.9

18:00:00 21.7 4 29.5 32.3 17

19:00:00 21.4 0 28 31.2 16.8

20:00:00 21.3 0 27.8 29.3 16.9


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Computer Lab 3rdFloor IC

Time Room Temperature Number of People Glass Temperature Air from vent

08:00:00 24.2 7 26.4 17.1

09:00:00 25.1 72 26.6 16.9

10:00:00 24.8 71 27 17.111:00:00 24.5 67 27.5 17

12:00:00 24.1 3 28.2 17.2

13:00:00 24.1 0 31 16.9

14:00:00 26.2 69 33.2 17.1

15:00:00 24 69 34.6 17

16:00:00 24.3 63 34.9 17.2

17:00:00 23.8 4 35.9 16.9

18:00:00 23.6 0 35.4 17.1

4thFloor Public Area IC


08:00:00 24.1 7 38 18.8

09:00:00 24.4 6 40.1 19.1

10:00:00 24.7 9 42.3 19.2

11:00:00 25.2 4 42.5 19

12:00:00 25 7 42.4 18.9

13:00:00 24.9 8 41.8 18.9

14:00:00 24.7 11 41.1 18.8

15:00:00 24.2 3 40.4 19.2

16:00:00 24.1 1 39.2 19.1

17:00:00 24 1 38.4 19

18:00:00 23.9 1 37.1 18.8

19:00:00 23.7 5 35.2 18.5

20:00:00 23.5 1 31.5 18.4

21:00:00 23.1 1 28.4 18.3

4thFloor 04 Classroom IC


08:00:00 25.2 56 38 17.3

09:00:00 26.1 57 40.1 17.1

10:00:00 25.8 57 42.3 16.910:15:00 25.4 5 42.3 17

10:30:00 26 53 42.4 17

11:30:00 25.8 53 42.5 16.8

12:30:00 25.7 54 42.2 17.1

12:45:00 25.4 0 42 17

13:00:00 26 48 41.8 17.1

14:00:00 25.4 48 41.1 17.2

15:00:00 25.2 49 40.4 17.1

15:15:00 24.9 17 40.3 17

15:30:00 25.1 47 40.1 17.1

16:30:00 24.8 45 39 17

17:30:00 24.6 37 38.1 16.9

18:00:00 23.9 0 37.1 17


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In the Innovation centre- the most significant source of heat is the sun. The number of people

in this building on any given day rarely exceeds 150. And the days the loads are high it is due

to classes on the 5thfloor where the trend can again be mapped. The zones of heat therefore

are clearly the glass faades that are exposed to sunlight through almost all the day as the

building is aligned along the north-south direction. Each side of the building gets nearly 6

hours of direct heat from the sun, sending the glass temperature to 43oC and more sometimes.

This temperature can be felt as the spaces heat up noticeably and only cool down once the

sun has set. The east facing faade though tends to get warmer as the brunt of the morning

sun heats it. Also though the NLH covers for a small part of the morning, it is not significant

in the grand scheme of the trends.

The data below shows the water temperature from the inlet and outlet of the chiller plants and

shows a direct correlation with the above data, proving a trending pattern of loads

Time Temp Inlet Temp Outlet

09:00AM13.5 10.8

11:00AM12.1 9.4

01:00PM

11.1 8.4

03:00PM10.9 8.7

05:00PM10.2 8.2

07:00PM9.5 7.9

09:00PM8.9 7.4

While studying and measuring these systems, it was noticed that certain parts of the system

needed thorough maintenance and the piping did in fact have scope for improvement. ThePlant is located behind the library and is also exposed to sunlight till almost 2:00pm. The

cooling towers, which are on top of the plant thus take direct heat from the sun for a

significant portion of the day, also when the load inside in maximum. The piping from the

towers that leads into the plant housing, though insulated, is painted black. The outer

temperature of this piping, when measured, was nearly 48 degrees Celsius which leads to the

conclusion that heat lost by the water in the tower would be slightly regained in the piping.

This was confirmed by the temperature difference in the water in the tower and the

temperature sensor checking the water as it enters the condenser and showed a difference of


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about 0.2-0.4 degrees. As the length of the piping is not significantly long enough for such

losses, the insulation is therefore not effective.

The cooling towers were also facing corrosion and had a great degree of eutrophication lining

the upper and lower tank. This was noticeable in the first and less in the consecutive tank.

The algae in the system would causing clogging and lining along the pipes would corrode and

also become ineffective for heat transfer in the system.

5. CONCLUSIONS AND SCOPE OF FUTURE WORK

5.1 InferencesThe following inference can be drawn from the above data and trends:

5.1.1 Load and Number of People

The load a system bears and therefore the room temperature rise in a system is a direct

function of the number of people in the room or hall. This is a fairly obvious inference

however the behaviour of the pattern is worth taking notice of.

The pattern itself goes to show the actual temperature of the surrounding directly trails behind

the appearance of load, i.e. the room gains heat as the number of people increase. This sudden

rise can be directly countered by altering when and how the system cuts off.

At low load times the system cuts off as the room has reached a desirable temperature and

allows the room to heat up so as to allow the cooling to start up again. However when a

sudden increase in load happens at time like this the system has to work twice as hard to

ensure the room/hall return to regular comfortable temperature. Therefore increasing the

energy consumed. The same way once the load suddenly drops the room cools more rapidly

and often beyond the set point to a colder temperature, before the cut-off kicks in. therefore

extra work is again consumed.

5.1.2 Solar Gain

The relation between heat gained and solar exposure is a direct one and one that does not

need noting. However it the location and the generation of increased heat zones that must be

noted.


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Solar gain does not affect the entire building in one go. It effects the side of the building that

is directly exposed to sun light. This allows for us to realise that a direct pattern for the

generation of heat zones based on time can be made so as to effectively counter the heat and

ensure maximum cooling. The system can also be taught to understand the shift in solar

pattern with seasons and time of year so as to know where the zone of heating will will shift

and increase during certain months.

Also cooling during day requires higher energy while the need reduces after sunset as the air

surrounding the area to be condition cools down as well. All of these things can be taken into

consideration to create a pattern for solar gain and loads.

5.1.3 Climatic Variation

The climate of an area also plays a key role in how much load the system must endure. The

current climate that the given system must endure is one of sever heat. This directly reduces

the performance of the system as external temperature to be overcome is higher and also the

temperature the condenser and cooling towers must combat is higher as well.

During the next semester however, once the rains start the system will have a lower loads as

the outside air will be much cooler and also damper. The system can thus learn when the

climate is forbidding and when it aids the system as a whole. Under this parameter the

laxities of how much energy can be conserved can be wither strict during low load times or

lenient during high load times such as summer.

The weather also helps play a significant role in the load on the system. Though it follows a

pattern the climate sets it has a very many random variables such as winds, cloud, sparse or

sudden rain, etc. that cannot be tracked easily and even if data is sent directly to the system

via the internet, the actual weather over the current location cannot be accurately mapped or

made a trend of. Though the current conditions can be easily sensed through appropriate

sensors placed strategically.

5.1.4 Insulation and System Maintenance

The systems current situation went show that it required strict maintenance. The cooling

towers need cleaning. The piping can be directed better to reduce solar exposure and

environmental exposure. The thermostatic sensors placed in the AHU can be made more

effective or in the case they are broken should be replaced.


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The building of glass and dark coloured paint are more susceptible to heat from the outside

and more likely to retain heat as well. All of these factors play a key role in how the tangible

and fixed characteristics of the building itself can reduce the effectiveness of the system and

increase load on it.

5.2 Improvements and Future Design Considerations

The following list of improvements and design considerations can help reduce the energy

consumption by the HVAC system. These use both direct solutions to tangible problems in

the system as well the trends and algorithms to be set in place in the software.

5.2.1 Improvements

The following improvements can be implemted on HVAC systems in general:

Graduated control valves for chilled water delivery to building and AHUs

o This allows for a controlled amount of chilled water to enter the cooling grate

of an AHU instead of a complete cut-off. These will allow for a cooling to be

provide to an area at controlled fractions so as to optimise energy usage. The

same way depending on the load on the building a supply valve can control the

amount of chilled water being directed towards it.

Speed controller for fans in AHUs

o These allow the system to maintain a changeable air delivery system that on

peak loads can deliver the maximum supply of air and cool the area rapidly

and also increase circulation. However at lean time it can be used coupled with

the graduated chilled water valve to deliver controlled cooling.

Reflective Surfaces on glass to reduce IR heat gain.

Load segregation in air ducts leading from AHU

o Some spaces are often divided into smaller spaces occupied by fewer people,

this causes these smaller spaces to cool faster. However since they have a

centralised AHU for these places the cut-off cannot be made on the whole

system on account of one smaller space. Therefore a simple load segregation

system can control either dynamically or statically the cooling being provided

to such an area. A static system would involve using smaller pipes that are

baffled to reduce flow and provide accurate cooling

Arrangement to allow Free cooling


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o Free cooling can easily reduce the amount of energy consumed by the system

and help drastically improve performance. A simple inlet from the outside

surroundings with humidity control can be used to create the use of free

cooling.

Directing pipes underground to act as heat sink

o Pipes directed underground from the cooling towers can lose some extra heat

thereby increasing the effectiveness of the cooling towers. This extra length of

pipe can help improve the performance of the system as the extra heat can be

given away to the ground. Also this improves the insulation capacity of the

pipes they dont gain heat from direct sunlight or hot air it comes in contact

with.

Array of sensors to check weather

o This array of sensors would directly guide the system in real time as where the

load will shift and if the weather will permit for any saving of energy. The

sensors in play would be, a radiosity sensor to check solar exposure and

clouds, humidity and wind gauge to check for wind, chance of rain and a

thermometer to check ambient temperature. These sensors would be placed on

top of the buildings to prevent any obstructions and for clear and direct

measurements.

RF-Id tag on people suing the space

o This measure is usually possible in a work place where employees/students are

given ids and can be used to track real time the presence of people in an area.

Coupled with the algorithms for trends of personnel usage, updates to the

current loads can be made adequately.

Locating vents and thermostats appropriately

o

This allow the system to channel the cold air and suck warm air most

effectively. A good pattern of circulation the takes into account significant

heat zones can increase performance of the system. Also the thermostats

placed in the correct inlet valves give a correct reading of the room

temperature and thereby reduce unnecessary cooling or heating of the room. It

also prevents heat zones from developing when placed strategically.

Manual over-ride in the Space being conditioned and in the BMS

Strict regime of system maintenance and redundancy


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o Proper and appropriate maintenance of any system can

5.2.2 Algorithms and Trends

With the above tangible improvements in place the following algorithms can be put in place

to ensure the system conserves maximum energy.

People

o The trend for the number of people as shown in the report can easily be

mapped for a space that is used every day. With this trend the system can

predict when a load might appear and when the loads will most likely reduce.

Based on the above trend the BMS can control the graduated AHU valve for agiven space and provide the optimum cooling needed. It would pre-emptively

cool areas expecting high load and reducing cooling in areas expecting a

reduction in load. If RF-id tags are available for tracking, the algorithm would

have real-time support for accurately changing and the needs for the given

space.

Solar gain

o

The algorithm for the above would dictate the extent of cooling given y thecontrolled fan so as to circulate a major portion of the air towards the heat

zone and sweep away the heat and all-round cool the area faster while

removing the liable heat zone from increasing direct load on the cooling grate.

This coupled with the trend from personnel usage would allow the system to

judge the peak loads acting on the system and accordingly allocate cooling

water better to the appropriate areas i.e. the graduated valves for buildings can

be used to direct flow to a specific building in high use while away from a

building in low use.

Climate

o This algorithm would dictate the need for free cooling or the need to shift the

strictness of the energy saving algorithms. As mentioned above this would

direct based on a pattern of climate noticed before

Weather

o Using the sensors and climatic patterns an algorithm in place can directly use

the given data to shift usage and requirement patterns to conserve energy, e.g.


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if the sensors dictate long term cloudy weather the cooling directed at

windows can be reduced so as to direct the system to respond to real time load

changes.

Over-ride requests

o Any system that has a high level of automation must have secure and

important over-rides in place in case the system has predicted the pattern for

usage in the wrong manner or has malfunctioned. These over-ride requests can

be handled by the operator of the BMS and manually over-ride the system to

meet the requested requirements.

5.3 Scope for Future Work

A deeper more thorough study of HVAC systems usage and components could lead to better

design considerations for future systems. This could help benefit current systems and the

study can extend to help improve pre-installed systems. Since changing systems currently in

place is difficult and more expensive the study can extend to understand more cost effective

ways to improve pre-installed systems.

The study can also extend to other systems such as lighting, hot water supply, etc to see the

maximum possible energy conservation and aim to make systems in large spaces such as

offices most efficient and save on costs of energy.


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References

http://www.brighthubengineering.com/hvac/859-factors-affecting-hvac-designing-and-heat-

load-calculations/

http://www.teriin.org/ResUpdate/reep/ch_5.pdf

http://www.intertek.com/hvac/performance-testing/

http://built-envi.com/portfolio/hvac-system-operational-characteristics/

http://www.brighthubengineering.com/hvac/26100-hvac-system-what-is-a-zone-part-

one/?cid=parsely_rec#imgn_1

Documents

Study of Automation of HVAC System and Component Improvements for Improved Performance