Dr. Miguel Zamora García

INDEX

INTRODUCTION

CASE 1: AIR-WATER HEAT PUMP

CASE 2: WATER-WATER HEAT PUMP

CASE 3: DHW BOOSTER HEAT PUMP

CONCLUSIONS

INTRODUCTION

The NxtHPG project involves the following participants: • two compressor manufacturers: Danfoss CC and DORIN; • two heat-exchangers manufacturers: LU-VE and ALFA-LAVAL; • two heat pump manufacturers: CIAT and ENEX; • highly qualified research institutions:

• UPVLC (Universidad Politécnica de Valencia), • KTH (Royal Institute of Technology, Sweden), • ENEA (Italian National Agency for New Technologies), • UNINA (Università degli Studi di Napoli Federico II), • NTNU (Norges teknisknaturvitenskapelige universitet) • EPFL (École Polytechnique Fédérale de Lausanne).

• the European Heat Pump Association who is in charge of dissemination activities.

“Next Heat Pump Generation” (NxtHPG) (www.nxthpg.eu) is an European project, whose main objective is the development of five reliable, safe, high efficiency and high capacity heat pumps (>35 kW) working with the two most promising natural refrigerants: Hydrocarbons (HCs) and CO2.

This paper presents a description of the HC prototypes development

CASE 1: Air-water heat pump • Air-water heat pump • Reversible cycle • Inverter compressor • Includes a desuperheater for DHW

production

Air: 7ºC (6ºC WB) Water: 40ºC/45ºC

Air:35ºC Water: 12ºC/7ºC

Rotation speed: 30Hz, 40Hz, 50Hz, 60Hz

CASE 1: AIR-WATER HEAT PUMP PROTOTYPE

3,7

3,75

3,8

3,85

3,9

3,95

4

4,05

4,1

0

5

10

15

20

25

30

35

40

45

50

30Hz 40Hz 50Hz 60Hz

CO

P

He

atin

g C

apac

ity

[kW

]

Heating Capacity COP

SIMULATIONS: HEATING MODE

COP improves by 3.38% while the heating capacity decreases by 38.7%.

Nominal conditions (50 Hz): HeatCap=40.09 kW ; COP=3.92

CASE 1: AIR-WATER HEAT PUMP PROTOTYPE

2,9

3

3,1

3,2

3,3

3,4

3,5

3,6

3,7

3,8

3,9

0

5

10

15

20

25

30

35

40

45

30Hz 40Hz 50Hz 60Hz

EER

Co

olin

g C

apac

ity

[kW

]

Cooling Capacity EER

Nominal conditions (50 Hz): CoolCap=34.76 kW ; COP=3.41

SIMULATIONS: COOLING MODE

CASE 1: AIR-WATER HEAT PUMP PROTOTYPE

DESIGN

Component Manufacturer Observations Filter drier Danfoss It can be used with propane, biflow Sight glass Danfoss It can be used with propane Axial Fan EBM Electronic Fan ATEX

Liquid receiver ESK Specific for propane Expansion valve Carel Electronic valve and ATEX, mono-flow

Check valve Danfoss It can be used with inflammable refrigerants Reversing valve Danfoss-Saginomiya

Presostat Danfoss Specific for propane

Main refrigerant components used in air-water prototype are:

CASE 1: AIR-WATER HEAT PUMP PROTOTYPE

IMAGES

CASE 1: AIR-WATER HEAT PUMP PROTOTYPE

IMAGES

CASE 1: AIR-WATER HEAT PUMP PROTOTYPE

CASE 1: AIR-WATER HEAT PUMP PROTOTYPE

PRELIMINARY TEST

A climatic chamber has been built at KTH Laboratory

CASE 2: Water-water heat pump • Reversible cycle • Two compressors in tandem • Includes a desuperheater for DHW

production

Part load

ratio

OUTDOOR HEAT EXCHANGER

Inlet/outlet water temperature

INDOOR HEAT EXCHANGER

Inlet/outlet water temperature

Sim1 100% 0/-3 ºC 40/45 ºC

Sim2 88% 0/ a ºC b /43 ºC

Sim 3 54% 0/ a ºC b /37 ºC

Sim4 35% 0/ a ºC b /33 ºC

Sim 5 15% 0/ a ºC b /28 ºC

Part load

ratio

OUTDOOR HEAT EXCHANGER

Inlet/outlet water temperature

INDOOR HEAT EXCHANGER

Inlet/outlet water temperature

Sim 1 100% 30/35 ºC 12/7 ºC

Sim 2 74% 26/ a ºC b /7 ºC

Sim 3 47% 22/ a ºC b /7 ºC

Sim 4 21% 18/ a ºC b /7 ºC Simulations done with one compressor and with two compressors

CASE 2: WATER-WATER HEAT PUMP PROTOTYPE

SIMULATIONS: HEATING MODE

0

1

2

3

4

5

6

100% 88% 54% 35% 15%

CO

P

2 compressors 1 compressor

0

10

20

30

40

50

60

100% 88% 54% 35% 15%

He

atin

g C

apac

ity

[kW

]

2 compressors 1 compressor

Capacity is higher than the behaviour with 2 compressors since 1.73% until 3.14%. COP is higher with one compressor since 2.81% until 3.66%

The performance of the heat pump with one compressor is slightly higher than the half of the nominal when using with two compressors

CASE 2: WATER-WATER HEAT PUMP PROTOTYPE

SIMULATIONS: COOLING MODE

0

10

20

30

40

50

60

70

100% 74% 47% 21%

Co

olin

g C

ap

aci

ty [

kW]

2 compressors 1 compressors

EER is higher when heat pump works with one compressor in 6.4% in nominal conditions and in 8.88% in 21%partial load ratio conditions.

The average of the improvement of cooling capacity with one compressor is 1.8%.

0

1

2

3

4

5

6

100% 74% 47% 21%

EER

2 compressors 1 compressors

CASE 2: WATER-WATER HEAT PUMP PROTOTYPE

DESIGN

Component Manufacturer Observations Filter drier Danfoss It can be used with propane, biflow Sight glass Danfoss It can be used with propane Expansion

valve Danfoss

Thermostatic valve specific for propane, biflow

Check valve None None

Reversing valve Danfoss-Saginomiya

Presostat Danfoss Specific for propane

Main refrigerant components used in air-water prototype are:

CASE 2: WATER-WATER HEAT PUMP PROTOTYPE

IMAGES

CASE 2: WATER-WATER HEAT PUMP PROTOTYPE

TEST BENCH:

CASE 2: WATER-WATER HEAT PUMP PROTOTYPE

Specific test bench has been built at KTH Laboratory

CASE 2: WATER-WATER HEAT PUMP PROTOTYPE

TEST BENCH:

CASE 2: WATER-WATER HEAT PUMP PROTOTYPE

SOME RESULTS. COMPARISON WITH SIMULATED VALUES:

Conditions:

Condenser inlet water temp 37.94

Condenser outlet water temp 44.83

Evaporator outlet water temp -0.5

Evaporator inlet water temp -5.43

Subcooling 3.38

Supeheat 9.2

CASE 3: DHW BOOSTER HEAT PUMP PROTOTYPE

CASE 3: • Water-water heat pump • Heat Source: Sewage water (10 to 15ºC) / Condensation loop (25 to 30 ºC) • Application: DHW production up to 60ºC

CASE 3: DHW BOOSTER HEAT PUMP PROTOTYPE

Operation principle is based on improve heat transfer taking advantage of increasing subcooling in the refrigerant side. This is something analogous to what is usually done in transcritical CO2 Heat Pumps

CASE 3: DHW BOOSTER HEAT PUMP PROTOTYPE

Prototype has been fully instrumented at UPVLC Laboratory. A test bench has been adapted.

TEST BENCH:

CASE 3: DHW BOOSTER HEAT PUMP PROTOTYPE

Cool Water Temp in =20ºC

DHW 55-60ºC Subcooling 8.6 ºC

DHW 10-60ºC Subcooling 43.9ºC

Condenser Heating Capacity

33.95 kW 34.49 kW

Subcooler Heating Capacity

1.00 kW 12.88 kW

Total Heating Capacity 34.95 kW 47.37 kW

COP 4.34 ±0.12 5.75 ±0.16

SOME TEST RESULTS:

CONCLUSIONS

Three propane heat pump prototypes have been designed and built and are now under test

Prototype 1 is an air-water reversible heat pump with an inverter compressor. Simulation predicts a COP increase of 3.3% in heating mode when reducing compressor speed from 50 Hz to 30 Hz, while in cooling mode it predicts a 11% of improvement at part-load (50 Hz to 30 Hz)

For the water-water prototype, simulations are able to predict the heating and cooling capacity measurements with 1% of relative error. However deviations are encountered in COP estimation (relative error higher than 6.5%) mainly due to the isentropic efficiency value used for modelling the compressor

Prototype 3 is a DHW booster heat pump. A novel concept of frigorific circuit based on subcooling control is now under test. Preliminary test results show significant COP improvements when the DHW is heated in counter current with a very high refrigerant subcooling

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