WO2001075379A1

WO2001075379A1 - Method and apparatus for increasing the effect in air heat pumps

Info

Publication number: WO2001075379A1
Application number: PCT/SE2001/000637
Authority: WO
Inventors: Tommy Sundqvist
Original assignee: Eversave Ab
Priority date: 2000-03-29
Filing date: 2001-03-23
Publication date: 2001-10-11
Also published as: SE518944C2; AU2001244929A1; SE0001118L; SE0001118D0

Abstract

Method and apparatus for increasing the effect in an air heat pump of the type comprising a compressor (1), a condenser battery (2) and an evaporator battery (3) and a system of tube coils (6-10) for transportation through the air heat pump of an easily evaporatable cooling medium/refrigerant, and in which heat is generated in the condensor (2) when passing cooling medium therethrough which medium has been heated by the compressor (1), and cooling medium in liquid phase is evaporated in the evaporator (3) while being recirculated to the compressor (1), or in which cold is generated, respectively, by reverting (20) the flow direction of the easily evaporatable cooling medium, and in which additional heat (13; 14) is arranged to be supplied at low outdoor temperatures at least at the cooled down output part of the condenser battery (2) and eventually also the output end of the evaporator battery (3).

Description

METHOD AND APPARATUS FOR INCREASING THE EFFECT IN AIR HEAT PUMPS

The present invention relates to a method and an apparatus for increasing the effect in an air heat pump By air heat pump is meant an apparatus comprising a condenser and an evaporator connected thereto, which are formed as separate batteries built on the principle that a cooling medium/refrigerant is brought to condensate and become evaporated, respectively, actuated by a compressor, whereby heat is generated when a cooling medium/refrigerant, which can easily be subjected to a phase convertion, is compressed from liquid to gas having an increased content of heat, which heat is transferred to air or a liquid passing through the condenser battery, whereby the hot gas becomes condensed, whereupon the relatively colder, liquid cooling medium/refrigerant is brought to evaporate in the evaporator after having passed an expansion valve and before being recirculated to the compressor for a new process cycle A problem in priorly known air heat pumps, in which the evaporator is generally placed outdoor, has been that the heating effect is strongly lowered at low temperatures It has been considered that the heat extracting function in such types of air heat pumps is strongly reduced at lowering outdoor temperatures and in practice becomes ceased at temperatures which are lower than about -5°C In an air heat pump according to the present invention the evaporator battery is placed indoor and is formed with a fan which blows out the cold issued by the evaporator outside the heated room, generally through a wall of the room or the house The air which is blown through the condenser and the evaporator is in part received from the indoor air, in another part from the outdoor air The advantage of said construction is that the air heat pump can give off effective heat at outdoor temperatures of as low as about -15°C

It has, however, been an aim to further increase the effect of air heat pumps and make it possible to economically run the air heat pump even at substantially lower temperatures, for instance at temperatures as low as down to -25°C or still lower temperatures, and in addition thereto to obtain a more economical running of the air heat pump than has so far been possible

According to the invention this has been made possible by an optimum controlling of the condensing and the evaporation process, respectively, at any specific temperature By supplying heat to the outlet side of the condenser the condensing of the hot gas coming from the compressor is postponed, whereby a more even condensing is obtained, meaning that the condensing process is increased so as to take place over the entire available condenser battery surface, and thereby that the heat emission is increased in the condenser, or that the heat supply to the evaporator is increased, respectively, and thereby that heat absorption is increased

The function of an air heat exchanger of said type is that the hot gas from the compressor is successively cooled during the passage thereof through the condenser coils, so that the gas in the part of the condenser battery which meets the heat collecting medium (air or water) first, in the following named the lower, or the later part of the condenser, is condensed into liquid phase of a successively decreasing temperature By supply of heat to the condenser coils adjacent the outlet of the condenser or to the lower condenser coils the temperature of the cooling medium/refrigerant is raised, not only in the latter or the lower condenser coils, but the heat is also spread over the entire condenser surface, so that a higher heat effect can be extracted A way of raising the heat in the latter or lower condenser coils is to mount one or more electric heater coils, as a type of effect raising means, so called "booster", between the condenser coils located closest to the outlet of the condenser, which electric heater coils can have a relatively moderate effect Preferably a first electric heater coil is mounted between the two last or lowermost condenser coils, and a second electric heater coil is mounted between the condenser coils located just above said first pair of coils, etc

The activation of the electric heater coils in the condenser and in the evaporator, respectively, can be made by an automatic operating control unit so as to obtain a maximum issued heating effect at different outdoor temperatures and exhaust air temperatures (from the building)

It is also within the scope of the invention to invert the flow direction of the cooling medium/refrigerant, so that the air heat pump alternatively can be used for cooling the indoor air Air heat pumps are known from e g SU 421 280, which patent discloses how a dielectric air flow is used for exchanging of heat, and in which the condensing temperature can be lowered by 3-5°C and thereby a certain saving of supplied electric current can be obtained

JP 2-103355 discloses an air heat pump/air cooler for a vehicle formed so that the amount of cooling medium/refrigerant used in the apparatus can be reduced, whereby a more effective air heat pump is obtained

DE 844 016 discloses a method of regaining part of the heat which is issued by a water cooled compressor, using liquid jets

None of said known apparatus solves the basic problems of the present invention, namely to increase the effect outputs in air heat pumps and to make it possible to economically run the air heat pump down to very low outdoor temperatures

Now the invention is to be described more in detail with reference to the accompanying drawings, in which figure 1 diagrammatically shows an air heat pump having a heating or alternatively cooling function, and figure 2 is a diagram showing the output effect of an air heat pump according to the invention, with and without effect increasing means ("booster")

The air heat pump illustrated in figure 1 generally comprises a compressor 1 for an easily evaporatable cooling medium/refrigerant, a condenser 2, an evaporator 3, an accumulator 4 for condensed cooling medium, an expansion valve 5 and a tube coil system 6, 7, 8 for the flow of cooling medium through the compressor 1 , the condenser 2, the evaporator 3, the accumulator tank 4 and the expansion valve 5 As conventional both the condenser 2 and the evaporator 3 are formed as upright or lying batteries having in zigzag formation extending cooling medium coils 9 and 10 respectively in which the cooling medium both in the condenser 2 and in the evaporator 3 enters one end of the coils, in the illustrated case the uppermost coil, and passes downwards from the top coil thereby meeting the heat receiving medium which passes from down and upwards in the battery, and which medium can be air or water. The function is as follows:

The relatively cold gas entering through the tube coil 6 at the lower part of the evaporator 3 is compressed in the compressor 1 to hot gas, which over the tube coil 6 is directed to the inlet end / the top of the condenser coil 9. An air flow 11 , or a liquid flow, is passed through the condenser battery 2, whereby the air or the water passing there through is heated by the hot gas in the coils 9 and is given off by means of the said air flow 11 to the room or the another space (not shown). As the hot gas passes downwards through the condenser battery 2 the gas is cooled and condenses more or less, so that the condensate leaves through the lowermost coil at the bottom of the condenser 2, mainly in liquid state, and is collected in an accumulator tank 4 from which the condensed liquid, which is still under pressure, passes through an expansion valve 5 or through a capillary tube, in which the pressure is lowered and the liquid is thereby transformed to gas form and leaves through a tube coil 7 at the upper end of the evaporator 3. An air flow 12 is blown through the evaporator and leads the air, which is thereby cooled down, out from the room or locality, preferably at an outdoor outlet. After having passed through the evaporator coils 10 the gas, which is thereby relatively cold, leaves through the tube coil 8 to the compressor 1 , in which a new working cycle is entered, starting with compression and heating of the gas.

As mentioned above the evaporator 3 is, in the illustrated case, preferably placed indoor, and the air flow 11 passing through the condenser 2 is to a part thereof received from the indoor air, to another part from the outdoor air, mixed in a fixed or controlled mixture relationship, whereby the air flow 11 will be partly tempered and the air heat exchanger can be run with heating economy down to relatively low outdoor temperatures, for instance down to between -(10-15)°C. In cold regions it may be desired to run the air heat exchanger with good economics to still lower outdoor temperatures. To this end an effect-matched, automatically controlled tube heater coil 13 is mounted at a suitable place at the part of the condenser battery 2 which meets the heat receiving medium first, for instance the air or the water, in the illustrated case at a suitable entering level above the bottom of the tube coil pack 9 for hot gas of the condenser battery 2. In figure 1 is shown, as an example, that a first electric tube heater coil 13 can be mounted between the lowermost and the lowermost but one condenser coil of the condenser 2, and that a second tube heater coil, in addition thereto, can be mounted between the above next following pair of condenser coils, etc. Each tube heater coil 13 is connected to an effect-matched control unit 15, which switches on the first and/or the second electric coil and successively following tube heater coils 13 as needed and depending on the outdoor temperatures. At low outdoor temperatures a condensing into liquid phase of the hot cold medium gases takes place at a relatively high level of the condenser battery 2, but depending on the action of the supplied electric heating 13 there is obtained a more effective condensing effect in that the gases of cooling medium/refrigerant, in the flow direction thereof, meet the electrically heated gases coming from underneath, whereby the cooling medium is maintained at such temperature that the gases do not condense to liquid phase, and whereby a higher operation temperature can be obtained over the entire condenser battery 2. This leads to an increased effect which is higher than the energy supplied by the electric heating.

It is also possible to mount two or more electric heater coils 14 at suitable levels in the evaporator battery, preferably adjacent the bottom outlet from the evaporator battery 3, in the illustrated case adjacent the bottom thereof, whereby there is obtained an increased evaporation and a heat reception of a suitable heat reception medium over the entire battery surface, even down to very low outdoor temperatures, like temperatures of down to -(30-40)°C, and whereby the increased heat at this place of the evaporator can melt the ice which will otherwise cover parts of the evaporator. This method also can be applied even in outdoor air heat pumps in which the evaporator is consequently placed outdoor. In figure 2 is shown a diagram over the effect given off by the air heat pump/exchanger, plotted along the Y axis, in relation to the outdoor air temperature, plotted along the x axis The base effect supplied to the air heat exchanger is shown by the line 16 This effect which emanates from the compressing of the cooling medium in the compressor 1 is relatively constant independently of the outdoor air temperature Curve 17 marks the effect given off by the air heat pump from about -30° up to about +15°C, from which temperature and further up the emitting of heat is of no interest It is obvious that the effect issued at low temperatures is very low in relation to the issued base effect 16 but that the gain of effect is increased following an increasing air temperature

Curve 18 shows how an additional effect is supplied using one or more electric coils 13 in the condenser 2 and using one or more electric coils 14 in the evaporator 3 Such supplied additional effect, which is in fact rather low, influences the totally issued effect according to a curve which is marked as line 19 The supplied "booster effect" gives a very valuable addition of effect at low outdoor temperatures but looses a substantial part of its effect at outdoor temperatures of more than about +15°C The control unit 15 supervises and switches on, upon need, one or more electric heater coils 13 and 14, respectively As mentioned above it is possible to use the above described air heat pump as an air cooling equipment, and this can be done by simply reversing the flow direction of the easily phase convertible cooling medium, for instance using a flow direction reversing means 20 comprising a 4-way valve so that the cooling medium is circulated from the compressor 1 to the incoming or lower part of the evaporator 3 and leaves through the output or upper part of the condenser 2 In this application the control unit 15 is switched off

Thus, the invention relates to an effect-matched air heat pump which is automatically run at effect maximum at any temperature of the incoming air from +15°C as far down as to, or close to -40°C This gives the air heat pump an improved efficiency, and in which the increase of issued heat pump effect at actuated "booster" is higher that the effect consumption of the booster, in particular at cold incoming air.

REFERENCE NUMERALS

1 compressor 1 1 air flow through condenser

2 condenser 12 air flow through evaporator

3 evaporator 13 electric heater coil (in 2)

4 accumulator tank 14 electric heater coil (in 3)

5 expansion valve 15 control unit

6 coil to condenser 16 supplied basic effect

7 coil to evaporator 17 issued effect

8 coil to compressor 18 supplied booster effect

9 condenser coil 19 total effect with booster

10 evaporator coil 20 flow reversing unit

Claims

C L A I M S

1 Method of increasing the issued effect in an air heat pump of the type comprising a compressor (1), a condenser battery (2) and an evaporator battery (3) and a system of tube coils (6-10) for the transportation of an easily evaporatable cooling medium/refrigerant through the air heat pump, and in which heat is generated in the condenser (2) by passing cooling medium gas therethrough, which medium has been heated by means of the compressor (1), and in which the cooling medium, in liquid state, is evaporated in the evaporator (3) while being recirculated to the compressor (1), characterized in that additional heat (13) is supplied to the condenser (2), at low outdoor temperatures, using one or more electrical heater elements (13) which are mounted between coils (9) in the part of the condenser which meets heat receiving medium (11) first (air or liquid) for increasing the condensing of the cooling medium over the entire surface of the condenser battery (2), so that a liquid phase of the cooling medium is received as close to the output of the condenser (2) as possible

2 Method according to claim 1 , characterized in that the switching on of the additional heater elements (13) is made automatically controlled (15) and matched to the effect at outdoor air temperatures of less than about +15°C 3 Method according to claim 1 or 2, characterized in that additional heat is supplied also to the evaporator (3) using one or more electric heater elements (14) which are mounted between coils (10) adjacent the output connection of the evaporator battery

(3)

4 Apparatus for executing the method according to any of claims 1-3 in an air heat pump of the type comprising a compressor (1), a condenser battery (2), an evaporator battery (3) and a system of tube coils (6-10) for transportation of an easily evaporatable cooling medium/refrigerant through the air heat pump, and in which heat is generated in the condenser (2) upon passage of cooling medium gas therethrough which gas has been heated by the compressor (1 ), and cooling medium in liquid phase is evaporated in the evaporator (3) while recirculating the cooling medium to the compressor (1), or in the opposite direction, respectively, when using the apparatus as a cooling apparatus, characterized in that the condenser (2) is formed with upright of lying batteries having horizontal or vertical tube coils (9), and in that the apparatus is formed with additional heating elements in the form of two or more electric additional heaters (13) which are mounted between pairs of condenser coils (9) at the cooled down (lower) part of the condenser battery (2) for foreseeing that the cooling medium gas is maintained in gaseous phase for optimum long period of time in the condenser (2).

5. Apparatus according to claim 4, characterized in that also the evaporator (3) is formed with electπc additional heaters (14) adjacent the output end of the evaporator (3) for melting, in case of cold weather, ice which would otherwise be formed on the evaporator (3).

6. Apparatus according to claim 4 or 5, characterized in that the additional heaters (13, 14) are controlled by effect-matching and effect-controlling using a control means (15) operating in dependence on the outdoor air temperature.