FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, .2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
AIR CONDITIONING SYSTEM;
BLUE—STAR -LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 195.6, WHOSE ADDRESS IS-KASTURI BUILDINGS, MOHAN T. ADWANI CHOWK, JAMSHEDJI TATA ROAD, MUMBAI - 400 020, MAHARASHTRA, INDIA.
THE "FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INENTION
The present invention relates to air conditioning system and more particularly to an improved air conditioner due to the amount of sub-cooling carried out in the system.
BACKGROUND OF THE INVENTION
Generally, an air conditioning system (AC) is an appliance for cooling or heating an indoor space, such as a residential space, a restaurant, an office room, etc. The air conditioning system comprises of a compressor for compressing a refrigerant into a high-temperature and high-pressure gaseous state, a condenser for condensing the refrigerant into a high-temperature and high-pressure liquid state, an expansion device for decompressing the refrigerant into a low-temperature and low-pressure liquid state, and an evaporator for evaporating the refrigerant passing through the expansion device into a low-temperature and low-pressure gaseous state. A refrigerant pipe connects the compressor, the condenser, the expansion device, and the evaporator.
Air is allowed to pass through the evaporator of the air conditioning system for cooling a room, thereby the air conditioning system discharges cold air to the room. Generally, the temperature of cold air is maintained between 22°C to 26°C and relative humidity of the said air is maintained between 40 to 60%. The condensed moisture is then drained out through the drainage system. Normally, one liter of water is removed in the form of condensate per TR (Tonnage of Refrigeration) of the AC for latent heat load of 30% and sensible heat load of 70% and the temperature of the drained or condensate water is around 7 to 10°C. If condensate water is directly drained out, loss of heat takes place due to the draining of condensate water.
Many attempts have been made to recover the loss of the heat with drained water by providing sub cooling to the refrigerant with drained water for example
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US patent 5327743 discloses a sub cooling condensate trap as an auxiliary unit for an air conditioning system, comprising a container having a heat exchange coil disposed therein and through which hot liquid refrigerant is passed, and water inlet and outlets in the container through which condensate water from the air conditioner condenser is passed counter currently to the refrigerant, thereby sub cooling the refrigerant and increasing the power usage efficiency of the air conditioning system. However, it requires providing a special arrangement to be made in air conditioner and also makes the air conditioner bulky and is auxiliary equipment.
Also there have been made some efforts in the prior art to use auxiliary cooling devices as subcoolers. In this effort for example, additional heat exchange coils are provided in the closed loop refrigeration system downstream of the condenser. This art includes attempts at providing subcooling units of the counterflow heat exchanger type as an add-on or retrofit for existing refrigeration systems or the like. A typical system utilizing a simple liquid cooling coil is shown in the U.S. Pat. No. 3,177,929.
But again for the above-mentioned invention one needs to provide an auxiliary cooling device that increases the complexity of the whole air conditioning system and also increases the cost however increasing the efficiency of the -overall system upto some extent
Hence it is desirable and there is a need of an air conditioning system, which apart from increasing the subcooling phenomenon is simpler in construction.
Also there is a need of such a system which improves the energy efficiency of the air conditioning system and that is easily maintained when cleaning of air or other maintenance procedures are carried out.
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SUMMARY
An object of the present invention is to improve the degree of subcooling in an air conditioning system.
Another object of the present invention is to provide an air conditioning system having a simple arrangement so as to make use of the lower temperature of condensate in order to improve the sub-cooling and subsequently the performance of the system.
Further object of the present invention is to obviate the problem as discussed in the background art of the invention.
According to one of the embodiment of the present invention an air conditioning system, comprises a compressor for compressing a refrigerant, a condenser for condensing the refrigerant coming out of the compressor, an expansion device to decompress the refrigerant coming out of the condenser, an evaporator to evaporate the refrigerant passing through the expansion device. A heat exchanger adapted in between the condenser and the expansion device, and a drain pan adapted at the bottom of the heat exchanger to collect condensate from the evaporator, wherein the heat exchanger is dipped in the condensate to provide sub-cooling to the refrigerant.
According to another embodiment of the present invention an air conditioning system further comprises a single fin and tube type heat exchanger having two portions wherein the two portions include an upper portion as the evaporator and the lower portion as the heat exchanger.
According to another embodiment of the present an air conditioning system, comprises a compressor for compressing a refrigerant, a condenser for condensing the refrigerant coming out of the compressor, an expansion device to decompress the refrigerant coming out of the condenser, a single fin and tube
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heat exchanger includes an evaporator and a heat exchanger as a sub-cooler, and a drain pan adapted at the bottom of the single fin and tube heat exchanger to collect condensate from the evaporator, wherein the heat exchanger -is adapted in between the condenser and the expansion device, and dipped in the drain pan.
Details of operation of the instant invention and further objects thereof will become evident as the description proceeds and from an examination of the accompanying drawings which illustrates embodiments of the invention in which similar numerals refer to similar parts throughout the several views.
A BRIEF DESCRIPTION OF DRAWINGS
Fig 1 shows a perspective view of an air conditioning system according to the present invention.
Fig 2 shows a sectional side view of the air conditioning system according to the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
In the following detailed description of the embodiments of the present invention reference is made to the accompanying figures 1 and 2, which in conjugation with this detailed description, illustrates and describes an arrangement to recover loss of heat due to draining out of condensate in an air conditioning system and to increase the subcooling of refrigerant circulating .therein.
According to one of the embodiment of the present invention an air conditioning system, comprises a compressor (10) for compressing 3 refrigerant, a condenser (20) for condensing the refrigerant coming out of the compressor an expansion device (30) to decompress the refrigerant coming out of the condenser (20), an evaporator (40) to evaporate the refrigerant passing through the expansion device (30), a heat exchanger (50) adapted in between the condenser (20) and
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the expansion device (30), and a drain pan (70)adapted at the bottom of the heat exchanger (50) to collect condensate from the evaporator (40), wherein the heat exchanger (50) is dipped in the condensate to provide sub-cooling to the
refrigerant.
A refrigerant pipe (not shown in the figure) connects the compressor (10), the condenser (20), the heat exchanger (50), the expansion device (30), and the evaporator (40). In the air conditioning system (100) the compressor (10) compresses the refrigerant into a high-temperature and high-pressure gaseous state, the condenser (20) condenses the refrigerant passing through the compressor (10) into a high-temperature and high-pressure liquid state. The expansion device (30) then decompresses the refrigerant passing through the condenser (20) into a low temperature and low-pressure liquid state and the evaporator (40) then evaporates the refrigerant passing through the expansion device into a low-temperature and low-pressure gaseous state.
Preferably a single fin and tube type heat exchanger (30) have two portions, an upper portion and a lower portion. The upper portion of the single fin and tube type heat exchanger (80) acts as the evaporator (40; and the lower-portion acts as the heat exchanger. The drain pan (70) is attached at the bottom of the single fin and tube type heat exchanger (80) to receive the condensate dripping from the evaporator (40). The hot air when passes over the evaporator (40) tubes gets cooled due to the sub cooled refrigerant circulating therein and gets converted in droplets and drips down towards the draining pan and gets collected over there.
The lower portion of the heat exchanger (80) rema ns dipped in the drain pan (70) having the condensate. Due to the low temperature of the condensate the refrigerant gets subcooled. The subcooled refrigerant further traverses towards the evaporator (40) via the expansion device (30) and provides cooling effect to the hot air passing over it.
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According to another embodiment of the present invention the fin and tube type heat exchanger (80) further comprises a plate (52) adapted at the bottom of the heat exchanger (50). The plate prevents the passage of air through the heat exchanger (50).
In the present invention the plate (52) is attached at the bottom of the heat exchanger (50) such that it covers the whole base heat exchanger (50) fin of the fin tube type heat exchanger (80) and such that no air passes over the said heat exchanger (50). The fin and tube heat exchanger (80) has inlet and outlet for the heat exchanger (50) and inlet and outlet for evaporator (40) along with a distributor (45) that distributes the refrigerant for each tube of the evaporator (40).
According to another embodiment of the present invention the evaporator (40) and the heat exchanger (50) are separated to each other.
As the liquid refrigerant is sub-cooled, it helps in further cooling when it passes through the expansion device (30). Also it is a fact-stated-by many compressor manufacturers that by improving the sub-cooling of liquid refrigerant by certain amount, there is an improvement in the overall capacity of the air conditioning system (100).
The air conditioning system (100) of the present invention does not require any special arrangement or construction or any major changes in the refrigeration circuit. The air conditioning system (100) of the present invention improves subcooling of the refrigerant cost effectively.
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Examples:
CASE:-1 (WITHOUT SUBCOOLING PROCESS THROUGH EVAPORATOR) Testing Conditions:-

Theory :
We have taken an R-22 Ductable split air conditioning unit with a Air cooled as our practical. For this unit an suction pressure of 75 FSIG is to be maintained in the evaporator. The evaporating temperature at 75 PSIG is 6.6 ° C.
We connected indoor unit to outdoor unit and filled the gas in the system after proper vaccumisation. We run the machine till the cycle is not balanced and maintained a suction pressure of 75 PSIG. The head pressure coming at this pressure is 280 PSIG.
We can say that the vapour condenses in the at 52 °C . But the liquid refrigerant coming out of is at 45 °C It means that there is some in-built sub-cooling in itself. So the sub-cooling from is :

Now the heat content of liquid refrigerant at 45 ° C at liquid saturated line of R-22 P-H chart is 24.14 kcal/kg. The head pressure will be same at 45 °C as 260 PSIG.

It means that there is no pressure drop here. Set the liquid refrigerant feed to TXV will be at 45 0 C .Now TXV is expanding the liquid refrigerant from high pressure to low pressure The suction pressure coming towards evaporator side is 75 SIG But in actual practice the suction pressure coming at inlet of compressor is 70 PSIG. But for calculation purpose we will consider 75 PSIG. As there is some pressure drop in evaporator coil, suction line .that we can not ignore. So the suction pressure at compressor inlet is 70 PSIG. The heat content at 75 PSIG is 12.62 kcal/kg, so the temperature to be reduced from 45 CC to 6.6 °C and the sensible heat to be removed from 26.5 - 12.62 = 13.38 kcal/kg
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P-H DIAGRAM W/0 SUBCOOLING THROUGH EVAPORATOR AND ONLY THROUGH CONDENSOR

But the liquid at 6.6 OC has an enthalpy of only 12.62 kcal/kg, that means an excess of 13.88 kcal/kg. So at the outlet of throttling device on reduction in pressure, a portion of liquid vaporizes, taking the latent heat of vaporization from the liquid itself(utilize excess enthalpy of 13.88 kca/kg) thereby cooling the liquid refrigerant to 6.6 ° C.
From the thermodynamic table of R-22 we find that the latent heat of vaporization of R-22 at 6.6 0 C is 47.7 0 C. But out of this 13.88 kcal/kg means 29 % of full latent heat at 6.6 0 C will have to be used for cooling the liquid from 45 0 C to 6.6 OC The total gas charged in 7.8 TR system is around 6.24 KG. So it means
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that 1.8 kg of liquid refrigerant burns immediately before entering in to
evaporator. So only 4.4 kg of liquid refrigerant take 48.19 - 13.88 = 34.31 as net
refrigerant effect.
So only 71% of liquid is available for useful refrigeration.
Total mass flow rate required for the system of 7.8 TR is:-
Total system capacity (TR) x one tone system capacity(kcal/min) / NRE (kcal/kg)
= 7.8x50.4/34.31 = 11.45 kg/min
Power required to produce this much of refrigeration:-
Mass flow rate (kg/min) x Work done by compressor (in sense of heat addition)
kcal/kg
So from fig -5 of P-H chart = 11.45 Kg/min x (h b - h a)
h b and h a are the enthalpies at compressor discharge and suction point ( B and
A)
So power consumed by the compressor is directly proportional to the mass flow
rate.
CASE : 2 (WITH SUBCOOLING EFFECT THROUGH CONDENSATE WATER OF EVAPORATOR)
Testing Conditions:-
IndoorSide : DBT : 27°C WBT:- 19 °C
Outdoor Side : DBT; 35 °C WBT :- 30 ° C
Theory :
Now as we have tested the system without the sub-cooling effect condensate
water of evaporator. But now we will run the same machine by providing sub-
cooling effect through condensate water of evaporator.
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How sub-cooling effect comes from condensate water of evaporator:
As in normal system, the liquid refrigerant comes after condensation from directly goes to Thermostatic Expansion Valve. There is sub-cooling effect but that is from the last rows of the after completely changed in to liquid. But here the liquid refrigerant comes from goes to the bottom rows of the evaporator instead of directly going to Expansion device.
But here main thing is that how sub-cooling effect is going on. As we know that in each evaporator, the water vapour presents in return air side gets changed to liquid form at dew point temperature and then that water collects in the drip tray. The temperature of that water collected :s around nearby to evaporator temperature. So here we are utilizing the cooling effect of that condensate water of evaporator. As it is constantly drained outside through drain pipe of drip tray as shown in fig-4.
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P-H DIAGRAM WITH SUBCOOLING THROUGH EVAPORATOR AND THROUGH CONDENSOR(INBUILT)

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Thus the liquid refrigerant coming from is at some high temperature and when it comes in contact with cold condensate water, then the temperature of liquid refrigerant comes down around 12 °C. It means that v/e are getting extra 12 °C sub-cooling effect other than sub-cooling from
Experiment test:
Now here we can run the system in the same conditions of performace test as specified. The discharge pressure coming is 275 PSIG and evaporating pressure of 75 PSIG. It means that vapour will condense at 49 °C temp in and liquid is evaporating at 6.6 ° C in the evaporator. But the liquid refrigerant coming out from is at 42 ° C. It means that a sub-cooling of 49-42 = 7 ° C is itself going to take place in the .
But after that we are passing the liquid refrigerant at 42 °C to the bottom portion of evaporator dipped in condensate water of evaporator .So the sub-cooling inlet temperature of evaporator is 42 ° C and the liquid coming out after sub-cooling is at 30 ° C. It means that we are getting sub-cooling effect through condensate water of evaporator.
42-30 = 12°C
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NRE (Net Refrigerating Effect improvement):
As the liquid refrigerant at the outlet of is at 42 ° C after sub-cooling effect from but the discharge pressure is maintained at 275 PSIG. So the heat content at 42 0 C is 23.5 kcal/kg But after getting the sub-cooling of 12 ° C through evaporator, the liquid refrigerating temperature is 30 ° C. As in case 1 of without sub-cooling through evaporator, the temperature was 45 ° C feeding to TXV. But here the liquid at 30 ° C will feed to TXV. Now the heat content at 30 ° C is 19.43 ° C and liquid refrigerant is evaporating at 6.6 ° C in evaporator and heat content at 6.6 ° Cis 12.62 kcal/kg.
It means that an excess of 19.43- 12.62 = 6.81 kca'/kg of heat is there, which will burn some part of liquid to bring down the temperature from 30 ° C to 6.6 ° C .As latent heat of vaporization of liquid at 6.6 ° C (75 PSIG) is 47.7 kcal/kg. And out of this 6.81 kcal/kg of heat is already used before refrigeration effect in evaporator. So only 47.7 - 6.81 = 40.89 kcal /kg of liquid refrigerant is available for useful refrigeration effect. Hence net refrigerating effect =40.89 kcal/kg , 85.72 % of refrigerant is useful here as compared to case 1 (without evaporator sub-cooling) of 71 %.
Mass Flow Rate improvement:
So from net refrigerating effect, we have seen that 40.89 kcal/kg of refrigerating effect is available for producing 1 tone of refrigeration effect. But the system is of 7.8 TR so the total net refrigerating effect will be 7.8 < 40.89 = 318.94 kcal/kg As 1 tonn = 3024 kcal/hr or 50.4 kcal/min ,so total mass flow rate will be:-50.4x7.8/40.89 = 9.61 kg/min
So 9.61 kg of refrigerant will be required per minute to flow in system.
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Power Consumption improvement:-
As power consumed by compressor is directly proportional to the mass flow rate
handled by compressor per minute.
= mass flow rate (kg/min) x work done by compressor in terms of heat Addition (kcal/kg) .But as mass flow rate is reduced so power consumption will reduce as compared to case-1 of without sub-cooling through evaporator.
CONCLUSION :
After observing the case study of without sub-cooling through evaporator (case-1) and . with sub-cooling effect through evaporator(case-2) from evaporator condensate water, we have concluded that following parameters have improved:-
1. NRE(Net Refrigerating Effect):-
NRE in case-1 = 34.31 kcal/kg
NRE in case-2 = 40.89 kcal/kg
▲ Improvement = 40.89 - 34.31 = 6.58 kcal/kg
So the net improvement in NRE is 6.58 kcal/kg, it means that the improvement of 19% in net refrigerating effect. But in actual practice it does not come 19 % as some of heat from liquid refrigerant gets added in to the supply air temperature of evaporator side and overall improvement comes down somehow.
2. Mass Flow Rate:-
Mass flow rate in case-1 = 11.45 kg/min
Mass flow rate in case-2 = 9.61 kg/min
▲ Improvement = 11.45 - 9.61 = 1.84 kg/min
So here the net improvement in mass flow rate 1.84 kg/min, it means that the Improvement 16% in mass flow rate. So '-6% less quantity of refrigerant to be fed to evaporator. So the overall gas quantity of refrigerant will reduce by 16 %. Hence compressor has to handle 16 % less refrigerant quantity, has to handle 16 % less refrigerant quantity and finally TXV has to throttle 16 % of less refrigerant
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3. Power Consumption-Mass flow rate in case-1 = 11.45 kg/min Mass flow rate in case-2 = 9.61 kg/min
▲ Improvement = 11.45- 9.61 = 1.84 kg/min or 16 %
As power consumed by compressor is directly proportional to the amount of refrigerant handle per minute but here the mass of refrigerant handled by compressor is 16 % less hence power consumption will reduce by 16 %.
The foregoing description of the invention has been se' for merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed tc include everything within the scope of the appended claims and equivalents thereof.
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WE CLAIM
1. An air conditioning system, comprising:
a compressor for compressing a refrigerant;
a condenser for condensing the refrigerant coming' out of the compressor;
an expansion device to decompress the refrigerant coming out of the
condenser;
an evaporator to evaporate the refrigerant passing through the expansion
device;
a heat exchanger adapted in between the condenser and the expansion
device; and
a drain pan (70)adapted at the bottom of the heat exchanger to collect
condensate from the evaporator, wherein the heat exchanger is dipped in
the condensate to provide sub-cooling to the refrigerant.
2. The air conditioning system as claimed in claim 1, wherein a single fin and tube type heat exchanger includes two portions.
3. The air conditioning system as claimed in claim 1 and 2, wherein the two portions include an upper portion as the evaporator and the lower portion as the heat exchanger.
4. The air conditioning system as claimed in claim 1 and 3, wherein the single fin and tube heat exchanger further comprises a plate adapted at the bottom of the heat exchanger so as to, prevent passage of air through the heat exchanger.
5. The air conditioning system as claimed in claim 1 and 4, wherein the single fin and tube heat exchanger have two inlets and outlets respectively.
6. The air conditioning system as claimed in claim 1 and 5, wherein one inlet and outlet is provided for receiving the refrigerant from (he condenser and
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the second inlet and outlet is provided for the passage of the refrigerant to the expansion device. 7 The air conditioning system as claimed in claim 1, wherein the heat exchanger and the evaporator are separate.
8. The air conditioning system as claimed in any of the preceding claims, wherein the heat exchanger is a single fin and tube type heat exchanger.
9. An air conditioning system, comprising:
a compressor for compressing a refrigerant;
a condenser for condensing the refrigerant coming out of the compressor;
an expansion device to decompress the refrigerant coming out of the
condenser;
a single fin and tube heat exchanger includes an evaporator and a heat
exchanger as a sub-cooler; and
a drain pan adapted at the bottom of the single- fin and tube heat
exchanger to collect condensate from the evaporator, wherein the heat
exchanger is adapted in between the condenser and the expansion
device, and dipped in the drain pan.
10. The arrangement as claimed in claim 1, wherein as described in the
preceding claims, description and drawings.
Dated this 21th day of December, 2006

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ABSTRACT
An air conditioning system, comprises a compressor for compressing a refrigerant, a condenser for condensing the refrigerant coming out of the compressor an expansion device to decompress the refrigerant coming out of the condenser, an evaporator to evaporate the refrigerant passing through the expansion device, a heat exchanger adapted in between the condenser and the expansion device, and a drain pan adapted at the bottom of the heat exchanger to collect condensate from the evaporator, wherein the heat exchanger is dipped in the condensate to provide sub-cooling to the refrigerant.
Reference figure 1.