AU2005232242B2

AU2005232242B2 - Active heat pipe implemented in the air conditioning system

Info

Publication number: AU2005232242B2
Application number: AU2005232242A
Authority: AU
Inventors: Budi Harjanto Listijono
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-10
Filing date: 2005-11-09
Publication date: 2011-03-31
Anticipated expiration: 2025-11-09
Also published as: AU2005232242A1

Description

56844 PAB:JPH P/00/011 AUSTRALIA Regulation 3.2 Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant: BUDI HARJANTO LISTIJONO Actual Inventor(s): BUDI HARJANTO LISTIJONO Address for Service: COLLISON & CO., 117 King William Street, Adelaide, S.A. 5000 Invention Title: ACTIVE HEAT PIPE IMPLEMENTED IN THE AIR CONDITIONING SYSTEM Details of Basic Convention Application: INDONESIAN Patent Application No. P00200500234 Dated 10 MAY 2005 The following statement is a full description of this invention, including the best method of performing it known to us: 2 TITLE - Active heat pipe implemented in the Air Conditioning system Technical Invention This invention is still related with the patent "heat pipe which is implemented in Air conditioning system" and also can increase the capability of the air 5 conditioning unit to condense even more water vapor, so that an even lower sensible heat factor/ratio (SHF/R) can be achieved. This Sensible heat factor is one of the criterions of performance in air conditioning system. The main difference between heat pipe mention in the patent "heat pipe which is implemented in Air Conditioning system" (later we call it passive heat pipe) 10 and active heat pipe is that: the amount of refrigerant flow in the passive heat pipe is constant whereas in active heat pipe is not, and the amount is vary depend on the requirement and it is controllable automatically. Background of Invention As we already know that the tropical area such as Darwin has a tropical 15 climate which is hot and humid. During a daytime the temperature and the humidity are very high; this condition creates thermally un-comfort for the occupants and will affect the productivity of the people. This type of condition not only occurs in Tropical area but also happens in a coastal area such as Brisbane, Sydney or Melbourne during summers. 20 If we follow ASHRAE Standard 55-2004 for Thermal Comfort Zone during summer, the operative temperature in the occupant room should have the temperature range from 230C - 270C and the relative humidity ranging from 30% ~60%. In order to achieve this condition an air conditioning unit which 3 has the capability to condense more water vapour is needed comparing with conventional air conditioning unit. In order to handle this hot and humid condition, a suitable type of air conditioning unit is needed to cup the high moisture contain. Basically this 5 new type of air conditioning unit is also equipped with such kind of heat pipe, however this heat pipe is not independent circuit like the one in the patent "heat pipe which is implemented in Air conditioning system" but is belonged to the subsystem of the whole air conditioning system. In this system, the heat pipe is activated by the solenoid valve to control the working fluid (refrigerant) 10 entering the reheat part of the heat pipe and the refrigerant is supplied by the compressor of the system. The basic principle of this active heat pipe is similar with passive heat pipe; it consists of 2 parts, pre cool part (evaporator part) and reheats part (condenser part), unlike the passive heat pipe which we can not control the amount of refrigerant flowing into the pre cool part or 15 re heat part, therefore the amount of condensate of water vapour also can not be controlled, consequently we also can not controlled the relative humidity in the conditioned room. In the contrary for active heat pipe the amount of refrigerant flowing into the re heat part is activated by the solenoid valve which it's open and close is controlled automatically by the humidistat, 20 therefore we can set the relative humidity of the conditioned room we want in this humidistat. The implemented of this active heat pipe in the air conditioning system is the development of previous passive heat pipe, patent "heat pipe which is implemented in Air conditioning system". This active heat pipe is a new 25 invention and firstly implemented in the air conditioning system in Indonesia. The main purpose of this active heat pipe is to achieve lower SHF/R (Sensible Heat Factor/Ratio) and to be able to control the relative humidity inside the conditioned room, so that the range of RH 35% - 60% in the 4 conditioned room can be controlled, whereas using conventional air conditioning as well as passive heat pipe air conditioning system can not do this. Unlike passive heat pipe, the flow of the refrigerant inside the passive heat 5 pipe is due to the temperature difference to create the density difference, in the active heat pipe the flow of refrigerant is supplied by the compressor of the main air conditioning system. Therefore there is no additional power input to drive this compressor, the only additional power input is to drive on and off of the solenoid valve which controlled the flow rate of the refrigerant entering 10 the active heat pipe. Brief description of the invention The construction of active heat pipe in the air conditioning system can be seen in figure 5, basically the arrangement of the active heat pipe is similar with the passive heat pipe, the cooling coil is placed in the middle of the 15 active heat pipe, the pre cool part of active heat pipe is placed facing the hot and humid air entering it, where as the reheat part of the active heat pipe is placed after the cooling coil, so that it will facing the cool air leaving from the cooling coil. The vapour refrigerant entering the reheat part of the active heat pipe is supplied by the compressor which compress the vapour refrigerant 20 from evaporator (low pressure) to the condenser of the whole system (high pressure), therefore the vapour refrigerant in reheat part of active heat pipe is hot and high pressure, it's pressure is the same with the condensing pressure of the whole system. Usually the condensing temperature in the air conditioning system is 500C (in passive heat pipe the temperature in reheat 25 part is ranging from 170C~190C), the amount of this hot and high pressure refrigerant vapour entering the reheat part of the active heat pipe is controlled by the solenoid valve (No. 8 of figure 5). This hot and high pressure 5 refrigerant vapour will release the heat to the cool air leaving from cooling coil (this air temperature is lower than condensing temperature) the vapour refrigerant inside the reheat part of active heat pipe will condense and change to a liquid form. This high-pressure liquid refrigerant before entering to the pre 5 cool part of the active heat pipe will be reduced its pressure by the capillary tube (expansion valve). Inside the pre cool part the refrigerant pressure is low, since the hot and humid air which is passing this pre cool part of active heat pipe has higher temperature than the evaporator temperature of the refrigerant inside pre cool part, then the low pressure liquid refrigerant inside 10 this pre cool part will start to evaporate and absorb some heat from the hot and humid air. The low-pressure refrigerant vapour from this pre cool part will go to the header of evaporator of cooling coil of the whole system. This low pressure refrigerant vapour will enter to the compressor and be compressed to higher pressure. This high-pressure refrigerant vapour will be distributed to 15 the condenser of the whole system and to the reheat part of the active heat pipe which is activated by solenoid valve which is controlled by humidistat. Therefore the condition of the air leaving this air conditioning equipped with active heat pipe can be controlled either the temperature as well as the humidity at the same time. The temperature is control by the cooling coil 20 whereas the humidity is control by humidistat which open and close the solenoid valve. Since the temperature of the refrigerant in the pre cool part of active heat pipe is lower than the one in passive heat pipe, therefore the reducing temperature of the hot and humid air before entering cooling coil is also bigger, this makes the cooling coil more capacity of the latent heat 25 cooling, and reducing more moisture contain in the air, consequently the SHF/R (Sensible Heat Factor/Ratio) of this unit is even lower than the passive heat pipe. The construction of this active heat pipe is the same with passive heat pipe, it consist of copper tube and aluminium fin as the extended heat transfer area. The refrigerant in active heat pipe is the same with the 6 refrigerant used in the whole system; it could be HCFC, HFC or Hydro Carbon refrigerant. Description of the figures Figure 1 5 Figure 1 shows the schematic diagram of an air conditioning system equipped with the active heat pipe. Main parts of the system consist of the followings: No.1: Cooling coil. No.2: Compressor. 10 No.3: Reheat part of active heat pipe. No.4: Expansion Valve. No.5: Indoor supply fan. No.6: Outdoor fan. No.7: Pipe branch. 15 No.8: Solenoid Valve. No.9: Reheat part of active heat pipe. No.10: Pre cool part of active heat pipe.

7 No.11: Capillary tube. No.12: Connecting pipe from compressor to solenoid valve. No.13: Connecting pipe from main condenser to expansion valve. No.14: Indoor unit casing. 5 Figure 2 Figure 2 shows the schematic diagram of conventional air conditioning system. Mains parts of this system consist of the followings: No.1: Cooling coil. 10 No.2: Compressor. No.3: Condenser. No.4: Expansion valve. No.5: Indoor supply fan. No.6: Condenser fan. 15 No.7: Indoor unit casing. Figure 3 Figure 3 shows the schematic diagram of active heat pipe to the cooling coil.

8 Mains parts of this figure consist of the followings: No.1: Cooling coil. No.2: Pre cool part of active heat pipe. No.3: Reheat part of active heat pipe. 5 No.4: Capillary tube. No.5: Expansion valve. No.6: Solenoid valve. Figure 4 Figure 4 shows the main parts of cooling coil before equipped with active heat 10 pipe. No.1: Cooling coil which consist of copper tube and aluminium fin. No.2: Distributor, to distribute equally the flowing of refrigerant to each circuit. No.3: Header, to collect the refrigerant vapour before entering the compressor. 15 No.4: U bent tube. No.5: Direction of air entering the cooling coil. No.6: Direction of air leaving the cooling coil.

9 No.7: Connecting pipe from pre cool part of active heat pipe to the header of cooling coil. Figure 5 Figure 5 shows the location of pre cool part of active heat pipe and reheat 5 part of active heat pipe toward cooling coil. No.8: Solenoid valve. No.9: Electric cable to supply the power to solenoid valve. No.10: Capillary tubes. No.11: Pre cool part of active heat pipe. 10 No.12: Reheat part of active heat pipe. No.13: Side plat. Figure 6 Figure 6 shows the whole combined unit of cooling coil (figure 4) and active heat pipe (figure 5) including the direction of hot and humid air entering the 15 pre cool part of active heat pipe and the direction of cool and dry air going out the re heat part of active heat pipe. Completed description of the invention The construction of the active heat pipe which will be installed in the air conditioning unit is shown in figure 5, basically the arrangement of this active 10 heat pipe is similar with the one in passive heat pipe, the pre cool part is placed before the cooling coil and reheat part is placed after the cooling coil, the difference are: In the passive heat pipe, there is no solenoid valve which will be activated on and off to let the hot and high pressure refrigerant vapour 5 to enter the reheat part; on the contrary in active heat pipe this solenoid valve is exist and it is controlled by humidistat and this humidistat is sensing the relative humidity of the conditioned room so that it will send a signal to open or to close the solenoid valve, this makes the relative humidity in the conditioned room will be the same as we want, in addition to that, in passive 10 heat pipe, there is no capillary tube to lower the pressure of liquid refrigerant from reheat part entering the pre cool part; In passive heat pipe the heat transfer either in pre cool part of re heat part is due to the temperature difference in their surrounding and it is no thing to do with the pressure of the refrigerant inside (both pressure almost the same) whereas in the active heat 15 pipe the heat transfer of the pre cool and re heat part is due to the pressure of the refrigerant inside them which crease the temperature difference with their surrounding temperature, in pre cool part the pressure is the same with evaporator pressure of the whole system and in the re heat part the pressure is the same with the condensing pressure in the whole system. These two 20 different pressures create two different temperatures inside those 2 parts which create the temperature difference with their surrounding temperature. Since the circuit of this active heat pipe is connected with the compressor and evaporator of the whole system, we can say that this active heat pipe is the sub system of the whole system. Therefore the process of vacuuming is 25 conducted simultaneously among the cooling coil and the active heat pipe. In order to optimise the heat transfer rate the pre cool part and re heat part are divided into several circuits, the hot and high pressure refrigerant vapour from compressor will be distributed to the condenser of the whole system and some part will be passed to the reheat part of active heat pipe through the 11 solenoid valve, the one goes to the reheat part of this active heat pipe will be condense by the cool air leaving from the cooling coil passed and reheat the cool air so that the relative humidity inside the conditioned room will be maintained, this high pressure liquid form of refrigerant will be lower down the 5 pressure same as evaporator pressure by the capillary tube (thermal expansion valve) when entering to the pre cool part of the active heat pipe. This low pressure liquid refrigerant will evaporate and absorb some heat from the hot and humid air passing this pre cool active heat pipe and make the hot and humid air temperature down (2 0 C~5 0 C) before entering the cooling coil. 10 Since some sensible heat of the hot and humid air is already taken away by the pre cool active heat pipe, therefore the cooling capacity of latent heat of this cooling coil will increase and this will condense more water vapour in the hot and humid air and make the moisture contain down. This cool and dry air will be reheat in the reheat part of active heat pipe as mentioned above, 15 whereas the low pressure refrigerant vapour in pre cool active heat pipe will enter the header of evaporator of cooling coil, from this header the low pressure refrigerant vapour will be sucked by the compressor to increase the pressure and temperature and distribute to the condenser of the whole system and some part go to the reheat part of the active heat pipe. The 20 process will repeat from the beginning. From the above explanation we can conclude that this active heat pipe will control the relative humidity actively following the setting of the relative humidity in humidistat, whereas the temperature will be controlled by the cooling coil, in other word this active heat pipe installed in air conditioning unit can be used to control both the 25 temperature as well as the relative humidity in the conditioned room actively. Since the temperature difference created by the low pressure in pre cool part and high pressure in reheat part are relatively higher than the one in passive heat pipe, therefore we can either choose big temperature reduction of hot and humid air in pre cool part to obtain higher condensation of the water 12 vapour to get lower relative humidity in the conditioned room by having more rows and more circuits in the pre cool part or we would like to have relatively small temperature reduction of hot and humid air in pre cool part by having one row and a few number of circuits, the reciprocal action should be applied 5 also in reheat part. With this high temperature difference between the air and the refrigerant, we can obtain relatively low of the relative humidity inside the conditioned room (35%~60%), few factor that influence the capacity of heat transfer in an active heat pipe such as: number of rows, number of circuits, pipe size connection and the size and the length of capillary tube (expansion 10 valve) and diameter of the pipe, height and length. The process in the air side can be explained as follows: Figure 6 shows the active heat pipe installed in a cooling coil, first the hot and humid air (27 0 C, 50% RH) is passing the pre cool part of the active heat pipe and cool down the temperature 2 0 C-5 0 C and becoming 220C-250C due to the evaporate of 15 the low pressure liquid refrigerant inside pre cool part and absorb the heat from its surrounding, this slightly cool air entering the cooling coil, this cooling coil will first absorb the sensible heat of the slightly cool air until this air become saturated and the water vapour in this air start to condense. Because some sensible heat of the air have been taken away in pre cool 20 active heat pipe, therefore the cooling capacity of this cooling coil will be concentrate in latent heat cooling and this will condense more water vapour to get lower relative humidity. The air leaving the cooling coil will be cool and dry with the temperature ranging from 80C-150C, this cool and dry air will enter to the reheat active heat pipe to increase the temperature by 2 0 C- 50C 25 and become 10OC-18'C, this air will be supplied to the conditioned room to cool the room as well as to absorb the moisture contain in that room to maintain the setting condition. The Sensible Heat Factor/Ratio (SHF/R) of this active heat pipe can be as low as 0.47. Figure 1 shows the refrigerant circuit 13 of active heat pipe installed in air conditioning system the hot and high pressure refrigerant vapour leaving the compressor (No. 2) is distributed to condenser of the whole system (No. 3) and through the branch pipe (No. 7) go to the solenoid valve (No.8), this solenoid valve is on and off based on the 5 signal from humidistat. From this solenoid valve the refrigerant enter into reheat active heat pipe (No.9) and condense into high pressure liquid refrigerant because of releasing the heat to reheat the air coming out cooling coil (No.1), and this high pressure liquid refrigerant is being lower the pressure by capillary tube (expansion valve No. 11) and enter into pre cool 10 active heat pipe (No. 10), in this pre cool the low pressure liquid refrigerant is evaporated and absorb the heat from hot and humid air, this low refrigerant vapour will combine with the low pressure refrigerant from the cooling coil (No.1) and enter into compressor. Figure 2 is the refrigerant circuit diagram of conventional air conditioning system. This figure 2 shows that the hot and 15 high-pressure refrigerant vapour going from compressor directly goes to the condenser (No.3 of figure 2); in this condenser that refrigerant gas will be cooled and condensed by ambient air. This high pressure liquid refrigerant goes to the expansion valve (No. 4) and being reduce the pressure and enter into evaporator (No.1) and this low pressure refrigerant will evaporate and 20 absorb sensible heat as well as latent heat of the hot and humid air which passing this evaporator and then that low pressure refrigerant vapour will be sucked and increased the pressure by the compressor. And the process will repeat. If we plot these two process in the psychometric chart that the sensible heat 25 factor/ratio (SHF/R) of active heat pipe is much lower that the conventional one or even comparing with passive heat pipe the SHF/R of active heat pipe not only lower than the ones of passive heat pipe but also it can vary this SHF/R depend on the load.

Claims

1. An air conditioning system including an active heat pipe, wherein the hot and humid air which is being conditioned will pass through a pre cool part of the active heat pipe and some of its sensible heat will be 5 absorbed by this pre cool part, and then enter a cooling coil, in this cooling coil the water vapour will be condensed reducing the moisture content of the air, this cool and dry air will be reheated in the reheat part of the active heat pipe before entering the conditioned room; this process is continuous until the desired relative humidity is achieved and a 10 humidistat activates a solenoid valve to close it, thereby preventing the hot and high pressure refrigerant vapour entering the reheat part of the active heat pipe, stopping the process.

2. The air conditioning system as in the immediately preceding claim further characterised in that the active heat pipe consists of 5 parts: pre cool 15 part, reheat part, solenoid valve, humidistat and capillary tube (expansion valve), wherein the cooling coil is place in the middle between pre cool part and reheat part, pre cool part is located before cooling coil so that the hot and humid air will pass this part first, whereas reheat part is place after the cooling coil, so that the cool and dry air 20 leaving cooling coil will pass this reheat part wherein solenoid valve is placed between a compressor and reheat part to control the flow of hot and high-pressure refrigerant vapour entering the reheat part wherein humidistat is place either in the conditioned room or return air duct to sense the relative humidity of the conditioned room so this humidistat 25 can be set the relative humidity as required with a capillary tube (expansion valve) placed between reheat part and pre cool part, this capillary tube is used to controlled and to lower down the pressure of refrigerant so that its has lower evaporating pressure. 15

3. The air conditioning system as in any one of the preceding claims further characterised in that the refrigerant supplied in the active heat pipe is part of the refrigerant of the whole system, it is also supplied by compressor to the solenoid valve and go to the reheat part, capillary tube 5 and pre cool part and then back to compressor.

4. The air conditioning system as in any one of the preceding claims further characterised in that the flow rate of the refrigerant entering active heat pipe is controlled by solenoid valve, and this solenoid valve is activated by humidistat. 10

5. The air conditioning system as in any one of the preceding claims further characterised in that the pre cool part and reheat part are made of copper tubes and aluminium fin as the extended heat transfer area and they consist of few circuits to distribute equally the amount of refrigerant to get better heat transfer rate wherein the high-pressure liquid 15 refrigerant from reheat part is connected to the pre cool part by capillary tube or expansion valve.

6. The air conditioning system as in any one of the preceding claims further characterised in that the air conditioning system equipped with active heat pipe has its goal to achieve better performance and lower SHF/R 20 without adding any electrical energy to reheat the air.

7. The air conditioning system as in any one of the preceding claims further characterised in that the air conditioning system equipped with active heat pipe is very suitable to be applied for the low relative humidity applications such as pharmaceutical, food processing, electronic 25 manufacturing etc. 16

8. The air conditioning system as in any one of the preceding claims further characterised in that the active heat pipe is very good to be applied for the conditioned room which has very high latent heat cooling such as meeting room, restaurant, supermarket, hypermarket, department store, 5 operating room, hall, church, and disco tic etc.

9. The air conditioning system as in any one of the preceding claims further characterised in that the active heat pipe is very good to be applied to the conditioned room which need to be controlled either the temperature as well as the relative humidity such as computer room, store room, 10 library etc.

10. The air conditioning system as in any one of the preceding claims further characterised in that the capacity of active heat pipe can be designed to suit the requirement by increasing either the number of the rows, circuits, heights, or the length of the reheat part and the pre cool part. 15

11.An air conditioning system as described in the specification with reference to and as illustrated in the accompanying representations. 17 Dated this 9th day of November 2005 BUDI HARJANTO LISTIJONO by his Patent Attorneys COLLISON & CO 5