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ENERGY CONSERVATION IN

WINDOW AIR CONDITIONERS

[1] Mir Aqueel AliAssociate professor Mech. Engg. Deptt.

B.N.College of Engg.Pusad.IndiaEmail –  mirakeelali@yahoo.co.in 

[2] Avinash WankhadeAssociate professor & Head Mech Engg Deptt

B N College of Engg Pusad. India

Email –  amwankhade@gmail.com[1] Corresponding author

ABSTRACT

Energy savings in a window air conditioner includes correctsizing of AC, purchase, better installation and operation coupled

with reduction in cooling loads. The design options for

substantial energy saving are related to increase in heat transfer

area, heat transfer coefficient, fan, ECM motor and compressor.The cyclic changes should be cared for using variable speed

compressors along with electronic expansion valves and fuzzy

logic controllers. Replacements of R22, (410a, 407c) already

commercialized are less energy efficient compared to R22. Thefuture AC will have better compressor and heat exchangers forimproved performance .

Keywords  – Energy, Window, Air conditioner, COP, EER.

ENERGY SAVING BENEFITS

Window AC accounts for about 50% of room AC market. Ason September 2006 the population of single phase ACoperating in India was around 5 million units. The industrygrew at the rate of 25 %, till the year 2010. The totalproduction in India was around 21.5 million units. These unitsrequired around 12000 MW of electrical energy in the year

2006 and 45000 MW of electric energy in the year 2010. If wehad improved the energy efficiency of room AC by 5%, wecould have saved approximately 2100 MW, which is

equivalent to two large size power plants.[1] Indian windowAC with an Energy Efficiency Ratio (EER) of 10.5 canimprove up to 11.2 used in US.[2,3]

The energy saving definitely will have the followingadvantages.1.  Foreign exchange for import of petroleum products will

reduce.2.  The global warming will reduce because of lower amount

of pollutants such as CO2, NOx and SO2 .3.  The environmental benefits such as water pollution and

erosion of land are viable due to reduction in base load andpeak load generation demand

SIZING OF AC-

One should go for cooling load calculation in order to arrive

for appropriate sized AC. A large sized air conditionerpenalizes in the following ways1.  It uses more energy.2.  It costs more to purchase than appropriate size AC.3.  The oversized AC cycles (on and off) more frequently

reduce its efficiency. Frequent cycling makes indoor

temperature to fluctuate more and results in lesscomfortable climate. It also inhibits dehumidification. It,in addition wears out the compressor and electrical parts

more rapidly. [4] The people having misconception of using two half sized AC, so that at least one will run incase of failure of other. It will result in an increase of 

running and initial cost.

PURCHASE

Today’s AC use 54% less energy to produce same amount of cooling as vintage AC used in mid 1970. Thus replacement is

an option for energy saving. Purchase energy star qualifiedAC which consumes at least 10% less energy than today’sconventional models. Its higher cost will be paid during itslife span. Purchase an AC with Energy saving features such as

i ) Digital readout for thermostat setting, ii) A built in timer,iii) A filter that slides out easily for regular cleaning. [5]

INSTALLATION

1.  Locate the AC in a window or wall near the centre of room on shadiest side of north or east facing wall. Directsunshine on condenser decreases efficiency by as much as

10%.2.  Minimize air leakage by fitting the AC snugly into its

opening and sealing gaps with Caulk (special sealants). 3.  Most TXV sensing bulbs are installed with no insulation

and improper contact and orientation. In these conditions,

hunting may arise (rapid opening and closing of thevalve) and harm the compressor while allowing liquid to

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enter the compressor in those conditions resulting inincrease power consumption. 

OPERATION

1.  Some units also use sophisticated sensors to detect thepresence of persons in the room to be cooled or heated andto direct the airflow in their direction. In correlation, a

mode sometimes called “Economic” can be associated:when nobody is in the room, the cooling or heatingoperation is stopped.

2.  Set AC thermostat settings properly, AC uses 3to5 percentless energy for each degree set above 22°C, therefore setthe thermostat as high as is comfortably possible insummer (25-27°c) [6 ]

3.  Fan speeds are available in 2 or 3 options. Set the fanspeed on high, except on very humid days. When humidity

is high set the fan speed on low for more comfort.Consider an interior fan in conjunction with AC to spreadthe cooled air more effectively through the room withoutgreatly increasing electricity use. Using fan allows you toset the thermostat temperature higher and thus reduces theenergy consumption. 

4.  Don’t place lamps or Television near AC thermostat. Thismay cause the AC to run longer.

5.  Use a voltage stabilizer to narrow the voltage variation.For each 1% voltage variation outside the narrow bandaround rating point causes energy consumption variationby 0.5 to 1% at normal conditions and 1 to 1.5 % under

adverse condition in a hermetic compressor.

MAINTENANCE

1.  The air filter, condenser and evaporator coils should beregularly cleaned with a blower. Some units also control

the air flow passage of the indoor unit by measuring thepressure loss to warn end-users when it is necessary toclean the filter.

2.  Use a fin comb to straighten the bent fins on evaporatorand condenser coil.

3.  In case of refrigerant leak evacuation should be done by

vacuum pump instead of compressor, used by mechanics.Use of vacuum pump ensures dehydration and removal of non condensable gases which may otherwise increasecondenser and evaporator temperature. This is in turnincreases energy consumption.

4.  Refrigerant charge should be optimum. Both under

charging and overcharging increase energy consumption.

COOLING LOAD REDUCTION1.  If possible go for passive cooling in the building before

construction.2.  Install window sun shade, storm windows, blinds or drapes

in front of glass, storm door, double or triple pane

windows.3.  The cool roof, attic, floor and wall insulation will reduce

the cooling load by 15%.

4.  Use compact fluorescent lamps (CFL) and fixtures whichconsume approximately 25% of electricity as compared tosimilar incandescent lamps and has 8 to 10 times longerlife.

DESIGN OPTIONS

INCREASE HEAT TRANSFER SURFACE AREA 

1. 

Increase Frontal Coil Area, 2.Increase Depth of Coil,3.Increase fin density, 4.Add sub cooler to condenser coil.

INCREASE HEAT TRANSFER COEFFICIENTS  1.  1. Improve fin design, 2. Improve tube design, 3.Spray

condensate on the condenser coil,4.Hydrophilic – film coatingon fins,5.Improve fan and fan motor efficiency

MICRO CHANNEL HEAT EXCHANGERS

IMPROVE COMPRESSOR EFFICIENCY

CYCLIC CHANGES

1. Variable speed compressor, 2.Alternative refrigerants, 3.

Electronic Expansion valves, 4.Thermostatic cyclic controls.

OTHER LOSSES

1.Side louver, 2. Divider wall heat loss, 3.Discharge airrecirculation heat loss, 4.Suction heat gain, 5. Reversing

valve, 6. Evaporative cooling, 7. Thermal Bridging

INCREASE FRONTAL COIL AREA

Enhancing frontal area in either of the coil results in increasedefficiency of the entire system. In order to have adequate

dehumidification at least 25% of the capacity should beallotted for dehumidification. The increase in frontal coil areaimproves evaporator performance thereby increasingevaporating temperature. The increased evaporatingtemperature results in inadequate dehumidification. Thefrontal area of coil cannot be increased beyond a limit because

it increases cabinet size.

INCREASE DEPTH OF COIL

Vertical tube rows may be at the most 3 or 4 because eachsuccessive row in a coil is only 70% effective as preceding

row. For systems working with R-410A, the trend is to usenumber of rows to 2 or 3 rows and for R-407C, it is possibleto take advantage of the temperature glide by using a

configuration with more than 3 rows. Addition of horizontal

row is limited by chassis size, issue of weight and refrigerantcharge.

FIN DENSITY OPTIMIZATION

Dominant heat transfer resistance is usually on the air-side. Fin density should be optimized with regards to improvement

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in heat transfer, effect on fan power; water drainage and dirtbuild up. The fin density is a function of type of coil(evaporator or condenser), fin type (wavy, louvered,enhanced), number of tube rows and tube diameter. 

SUB COOLER

A sub cooler can be added between condenser outlet and

capillary inlet and may be submerged near the condenser inthe condensate produced by evaporator. The addition of subcooler will increase the size of condenser coil. The addition

of sub cooler may be possible if adequate area is availableotherwise the size of window air conditioner will increasethereby resulting in increased initial cost. The increase inEER may be 1.4 to 3 % for various capacities.

IMPROVE FIN DESIGN

Enhancements to the fin design have the effect of improvingcoils air side heat transfer coefficient thereby improvement inoverall heat transfer capability of coil. The improvements arepartly due to increased air turbulence over coil caused byenhanced fin design. The fin improvement can be achieved

by using a corrugated or wavy fin pattern or a louvered orlanced fin pattern. Recent progress also includes decrease of 

the fin thickness.

IMPROVED TUBE DESIGN

The refrigerant side heat transfer coefficient with grooved

tubing is greater than that for smooth tubing. Improvement of refrigerant heat transfer coefficient with grooved tubing is afunction of width, height and spacing of grooves as well as oil

concentration within the refrigerant. The effect of refrigerantpressure drop should be optimized. In order for the heatexchange increase not to be too detrimental to the refrigerant

pressure loss in the heat exchangers, the diameter of thecopper tube is adapted to the refrigerant conditions, withlarger diameters for the gas state and lower diameters forliquid or two phase conditions. These measures also enable todecrease the refrigerant charge resulting in lower powerconsumption.

The system performance due to different heat exchanger finand tube designs data from Chinese texts on air conditionertechnology is given in Table 1 which summarizes the heattransfer and pressure drop enhancement factors.  The

enhancement factors are relative to flat fins and smooth tubing(i.e., flat fins and smooth tubing have heat transfer and

pressure drop enhancement factors of 1.0). The value used forthe heat transfer enhancement factor is the multiplication

factor for air-side heat-transfer coefficient of the coil. [7]

Table 1

Design Heat Transfer

Enhancement

Factor

Pressure drop

Enhancement

Factor

Evap Wavy Fin (smooth tube) 1.12 1.05

Evap Slit Fin (smooth tube) 1.5 1.2

Evap Slit Fin (groove tube) 1.8 1.2

Cond Wavy Fin (smooth tube) 1.11 1.05Cond Slit Fin (groove tube) 1.44 1.25

Cond Slit Fin (groove tube) 1.57 1.25

Evaporator Groove Tube 2.4 1.5

Condenser Groove Tube 2.2 1.4

SPRAY CONDENSATE ON CONDENSER COIL

There is a slinger ring at the condenser fan blade tips whichcollects and sprays small amount of condensate on condensercoil during fan rotation. Spraying condensate improves airside heat transfer coefficient but should be optimized for dirt

built up due to water accumulation. Typically, only a smallpercentage less than 25% of the condenser coil is actuallywetted by the spray because the fan can only sling water onthe first few rows of the heat exchanger

HYDROPHILIC – FILM COATING ON FINS

Fins with hydrophilic coatings have an affinity for watercausing condensed water to film the fin surface in a thin layer.The strong affinity for water results in less retention of bridgeshaped water drops between fin surfaces. According toresearch it causes the water drops to fall of the fin surface

quickly resulting in reduced air side pressure drops andincreased air flow rates across the heat exchanger. Thealuminum fins will not corrode due to separation of waterdroplets. Under dehumidifying conditions, hydrophilic typefin surfaces are reported to reduce air side pressure drop.Therefore cooling capacity is improved as compared to air

conditioning systems using untreated fins.

FAN & FAN MOTOR

The air delivery side of room air conditioner consists of onemotor driving two fans, one on evaporator side and the other

on condenser side. The evaporator fan is usually a blowerwheel (centrifugal forward curved fan) while condenser fan ispropeller typed. The evaporator and condenser fan motor

consume 5% and 7 respectively of total energy consumptionof room AC. Propeller fans previously made of processedmetals, are now made of plastics. The shape of blade must be

such that it should increase the volumetric efficiency anddecrease the noise level. Opportunities for conserving energyare also available by improving the efficiency of air deliverysystem and fan motor. In addition, improving fan motorefficiency results in additional compressor energy saving. Thisis due to lower heat removed by the heat exchangers becauseless heat is rejected by the fan motor. Earlier fan motors were

of low efficiency shaded pole typed but now permanent split

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capacitor (PSC) motors having efficiency in the range of 50%to 60 are used. Electronically commutated motors (ECM)have the efficiency in range of 70 to 80%. In an ECM poweris pulsed on and off electronically. By varying the timing andduration of pulses, the electronic controller can accomplish

speed control as well as maintain high torque at the start andover a broad speed range. [8] The cost of ECM is 2.5 to 5times more and increases by 0.4 as compared to PSC motors.

In a conventional AC, since there is a single motor, it runsboth the indoor and the outdoor fans. Hence, when the fanspeed inside reduces, even the outside fan speed decreases.

This reduces the machine's ability to throw hot air outside andimpacts the overall efficiency of the AC. If there are twoindependent fan motors one for the indoor fan and the otherfor the outdoor fan. The inside fan speed is independent of theoutside fan speed, and thus the ability of the machine to throwhot air outside remains unaffected. Energy saving is achieved

due to better cooling of condenser. [9]

MICRO CHANNEL HEAT EXCHANGERS

Micro channel heat exchangers (MCHX) use has beenrecommended in Energy star product specification for room

AC draft 1 version 3[10]. MCHX transfer heat throughmultiple flat fluid filled tubes containing small channels whileair travels perpendicular to fluid flow. Compared to fin tubeheat exchangers the air passing over the heat exchanger haslonger dwell time, increasing both the efficiency and rate of heat transfer. This advancement in heat exchanger technology

allows the MCHX to be smaller and yet have the sameperformance as a conventional heat exchanger, in other wordsimproved performance in same volume as that of conventionalheat exchanger. The smaller size of the exchanger reducesrefrigerant pressure drop, improving overall compressorperformance. However, micro channels also have weaknesses,

such as large pressure drop, high cost of manufacture, dirtclogging,and flow mal-distribution, especially for two-phase flows. Astudy of performance evaluation of a window room AC withmicro channel condensers by Man-Hoe Kim and Clark revealsthat refrigerant charge requirements can be decreased by

35%,which in turn reduces global warming (due to higherGWP of R410 a). The condenser core volume and weight can

be reduced by 55% and 35%. [20]. This technology is alreadyadopted by the car industry for more than 9 years  it has beenrecently adapted to mini chillers by Carrier.

IMPROVED COMPRESSOR EFFICIENCY

Compressors  are the heart of refrigeration system. Energyconsumed by the compressor is 80 % of window airconditioners total energy. System efficiency can be improvedsimply by utilizing more efficient compressors. Compressorefficiency is improved through the use of high efficiency

motors, high grade materials in the pumping mechanismcombined with advance production methods and equipment. Progresses have been made to reduce friction losses in rotary

compressors. The Swing compressor manufactured by Daikinhas the roller solidarized with the blade; this avoids leakagesbetween high and low pressure sides. The compressor has 15% higher global efficiency, but it also uses an improved DCmotor. Other manufacturers (Toshiba, Fujitsu, Sanyo) have

adopted a rotary compressor with two stages or twin rotarycompressor that enables to improve the efficiency by 10 %.[11] Advantages of scroll over reciprocating are 1 Highest

volumetric efficiency- approximately 100%, 10% to 20higher EER, 2 Low sound characteristics- approximately 5decibels lower than reciprocating , Smoother and continuous

compared to rapid piston movement which ensures lowvibration and lower discharge pulse 3 Outstanding reliabilitywith regards to lower failure rate and tolerance to liquidrefrigerant as well as debris.[12]Scroll compressors with three dimensional compression arealso experimented. They are (i) 35% smaller in size, (ii) 26%

lighter in weight, (iii) 5.5% more efficient and (iv) The noisegenerated is lowered by 6 DB as compared to conventionalone. [13]

VARIABLE SPEED COMPRESSORS

Power consumed by a motor varies as the cube of its speed. Acompressor working with variable speed motor and its speedmodulated to match the load offers the advantage of substantial reduction in power consumption and increase inEER by 1.2.Variable speed compressor matches the load in aroom. Rather than having only on off control, modulating the

cooling capacity can better match the required load.Advantages of variable speed compressors arei. Quieter Operation at low speeds.ii.  Enhanced comfort by eliminating large fluctuations in

room temperature.The control of variable speed compressors is accomplished

through the use of electronic ASD at the motor. Becauseelectronic ASD are compact and do not have to bemechanically coupled to motor, they can be applied tofractional size motors of room ACs. Inverter based ASD arecommon for induction motors while converter based ASD’sare used for ECM motors. ASD perform well both with rotary

and scroll compressors. A savings of 10% is possible withvariable speed compressor. A digital scroll modulates capacityfrom 10% to 100% significantly lowering energy consumptionwith the help of electronically controlled solenoid which loadsand unloads scroll members. [14]Although more efficient than single speed systems at full load

conditions. Because of parasitic losses associated with theelectronics required to operate variable speed compressor,they may actually draw more power at full load conditions.Thus, variable speed systems may exacerbate peak powerconcerns for electric utilities.

ALTERNATIVE REFRIGERANTS

EPA will ban the use of R22 after 2020 and production by2010. In addition to ODP, GWP and energy efficiency,

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refrigerant should be non toxic, non flammable, chemicallystable, inert etc. Even though, the ODP and GWP of refrigerant may be less still it may contribute to globalwarming due to reduced energy efficiency. R410 A (HFC 410A) is a binary blend of 50/50 by weight of 

HFC 32 and HFC 125 and is an alternative to meet themontreol protocol in the long term because of zero ODP. Ithas negligible temperature glide (less than 0.2 K over its

operating range), but has GWP- 2000, AEL-1000ppm. [15]Commercialization is complete. If used as a drop in substitutecapacity reduction and power increase are significant

[16].when used in new systems there is a very marginaldecrease in energy efficiency. An advantage of R-410A is thelower liquid density of the refrigerant (approximately 12%lower than for R-22). The refrigerant charge is thenapproximately 25 to 30% lower than the required charge of aR-22 system for comparable duty and efficiency.

Another Alternative R 407 C (HFC 407C) is a ternary blendof HFC  –  32/HFC-125/HFC-134a with composition of 23/25/52 % by weight. The temperature glide is (7.4

0) as well

as GWP-1700, AEL-1000ppm. This temperature glide leads toan impact on boiling heat transfer. The pool boiling heattransfer coefficient decreases as temperature glide increases.

This cycle of events decreases the heat rate transfer and theoverall performance. Moreover, since it is a non-azeotropicrefrigerant mixture, fractionation may occur in case of the leak in the system. Hence when leaks occur, the entire refrigerantmust be removed and new R407C fluid with the rightcomposition must be used. Inclusion of liquid to suction heat

exchanger in R407c retrofitted system has improvedperformance of window air conditioner in terms of refrigerating capacity, mass flow rate and COP, but hasreduced power consumption and pressure ratio. [17]

ELECTRONIC EXPANSION VALVES

As compared to capillary the thermostatic expansion valves(TXV) can adapt better to changes in operating conditionssuch as those due to variation in ambient temperatures, whichaffect the condensing temperature. Electronic expansionvalves (EXV) are controlled by either digital or electronic

circuits, they give additional flexibility to consider controlschemes that are impossible for conventional TXV .In airconditioners which have inverter driven variable speedcompressors, EXV can improve performance beyond that of TXV’s. EXV measures and controls the superheat of suctiongas as it leaves the evaporator (at saturated condition ) and

enters compressor, compared to the standard TXV whichcontrols the superheat of suction gas only up to the location of thermal bulb of valve mounted on suction line.   AdoptingEXVs in air conditioners enables an appreciable energy savingwith respect to the same installations equipped with traditionalTXVs. Another advantage of TXV and EXV over thecapillary is the ability to block refrigerant migration when the

unit is OFF or cycling ON-OFF, thus in power consumptionreduces at the start.

THERMOSTATIC CYCLIC CONTROL

Remote thermostatic cyclic controls accurately monitor roomtemperature than earlier built in thermostats. Fuzzy logiccontroller offers better comfort requirements. Efficiency gains

require coupling it with an improved air flow discharge anddistribution system.

OTHER LOSSES

I. SIDE LOUVERS

Side louvers have a significant impact on unit performance.Side louvers separate the airstreams to and from the condenserand reduce recirculation and enhance the movement of airover the outdoor coil. Units without side louvers operate at alower efficiency due to additional compressor power (around

4%) required for compensating the decreased air flow over thecondenser coil.

II. DIVIDER WALL HEAT LOSSES

Divider wall heat losses are composed of heat leakage (due to

temperature difference) and air leakage losses. Heat leakagesare controlled by Styrofoam insulation; they can be furtherreduced with better insulation which has higher soundblankets. Air leakage in indoor section takes place throughcracks and open spaces in divider wall. They should be triedto reduce with better damper arrangements.

III. DISCHARGE AIR RECIRCULATION HEAT LOSS

Short circuiting of discharge air into the AC reduces heatcontent of the mixture, thereby reducing capacity (around6%). The EER decreases since the energy input is same.

They can be reduced with better air delivery such as sidedelivery.

IV. REVERSING VALVEA reversing valve allows a room AC to operate as a heat pumpand provide space heating in addition to cooling. The

reversing valve adds an additional load to the system thatincreases the unit’s power requirement by an estimated 5% 

V. SUCTION LINE HEAT GAIN

It takes places due to motion of refrigerant from indoor to

outdoor section and hence capacity decreases. The heat gaincan be reduced by better insulation on suction line.

VI. EVAPORATIVE COOLINGA problem related with application of air condenser in hotweather conditions (about 50

oc) is related to the high storeyed

buildings. In these buildings the hot air from air conditioners

of lower story rises up and provides a hot flow field aroundthe air conditioners of higher storeyed. Sometimes, theincrease in the air temperature is so high that the air

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conditioner trip down. It is generally believed that the COP of an air conditioner decreases about 2% to 4 by increasing eacho

C in condenser temperature and the COP of an airconditioner could drop down as much as 40% in hot weathercondition. Energy conservation can be done by putting two

cooling pads on both sides of the air conditioner and injectingwater on them in order to cool down the air before it passingover the condenser. The experimental results show that

thermodynamic characteristics of new system are considerablyimproved and power consumption decreases by about 16%and the COP increases by about 55%.[18 ] 

VII THERMAL BRIDGING

Thermal bridging occurs when insulating material is“bridged” by a conductive material; for example by a AC witha metallic chassis that extends from the exterior to the interior

of the home. The AC forms a thermal bridge that conductsheat from the home in the wintertime and into the home in thesummertime. Energy conservation can be done by minimizingthis loss by using plastics instead of metallic sheets.

CONCLUSION

The various methods of energy conservation are discussed.The design adoption depends upon modification cost andenergy saved. Improvement in compressor EER may be thefirst priority followed by use of better heat exchangers.MCHX are not yet commercialized for window AC.

Government of India has taken a welcome step by makingBEE star label for room AC compulsory from January 2010.

REFERENCES

[1] Bhambure J M , Room ACs with Star Ratings ISHRAE Journal July – sept

2006

[2] Most efficient air conditioner.   American council for energy efficient 

economy as on 24/1/2011. 

[3] BEE labeled air conditioner version 2 august 2010

[4] Consumer energy information Energy efficiency and renewable energy

network fact s heet.

[5] Room air conditioner energy efficiency and renewable energy.

[6]Gu ide on energy efficient Room air conditioner

[7]. Technical and economic analysis of energy efficiency of Chinese room

air conditioner, February 2001 LBNL 4555O pp (29) 

[8] Electronically commutated motors Washington state university extension

energy program 

[9]. www.hitachi.comHome >Products> HomeA ir Conditioners > Window Air

Conditioners > Quadricool TM

[10] Energy star product specification for room AC draft 1 version3 

[11] ASHRAE handbook- systems and equipment 2008 (S I) Chapter 49 room

air conditioners pp (49.1 – 49.5)

[12] Scroll compressors presented by kirloskar Copeland ltd. at national

conference on RAC, Chennai.

[13] High efficiency and large capacity 3D scrol l compressors. GU series

. Mitsubishi heavy industries Ltd. Technical Review Vol .43 no. 2 (June

2006).

[14]. Liebert DS model with optional digital scroll compressor

[15] J,M.Calm and P.A.Domanski, R22 Replacement status ASHRAE Journal

46 (8):29-39,August 2004

[16]. Performance as sessment of HCFC-22 w indow air conditioner

retrofitted with R-407C S. Devotta a, A.S. Padalkar , N.K. Sane Applied

Thermal Engineering Volume 25, Issues,17-18 December 2005, Pages 2937-

2949 

[17] R.Vijayan and P S S Srinivasan influence of internal heat exchanger on

performance of window AC retrofitted with R 407C

Journal of scientific and indus trial research ol.68, Febraury2009, pp 153-

156

[18] Ebrahim Hajidavalloo A pplication of evaporative cooling on the

condenser of window-air-conditioner Applied Thermal

Engineering 27 (2007) 1937 – 1943

[19] Deve lopment of a linear compressor for air conditioners and heat pumps.

Warren D .Waldron (EPA .Project Summary).

[20] Man- Hoe- Kim and Clark, Performance Evaluation of window  Room ac

with micro channel condensers.