GB2066440A

GB2066440A - Heat Pumps

Info

Publication number: GB2066440A
Application number: GB7939676A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-11-16
Filing date: 1979-11-16
Publication date: 1981-07-08

Abstract

A heat pump has an evaporator coil (17) surrounding a housing which contains the compressor (16) and the motor for the compressor. The evaporator coil is connected to the housing by metal vanes. The evaporator coil may be located in an air duct or in a duct through which, in use, solar-heated water passes. The condenser coil (14) may be located in a water tank (19). <IMAGE>

Description

SPECIFICATION Heat Pump and Method of Supplying Heat A first aspect of the present invention relates to a heat pump comprising a condenser, an evaporator and a compressor connected in a closed circuit along which a heat transfer fluid is caused to flow, and a motor for driving the compressor.

When a heat pump is used for supplying heat to the interior of a building or other point of use, heat is transferred at the condensor from the heat transfer fluid to heat supply means which supplies the heat to the point of use. The heat supply means may be the condenser itself, for example where the condenser is adapted to dissipate heat into a room. Alternatively, the heat supply means may be a secondary fluid which carries heat from the condenser to the point of use.

During operation of a heat pump, heat is carried from the evaporator and from the compressor to the condenser by the heat transfer fluid and heat is also emitted by the compressor to its environment. Although thermal insulation of the compressor would reduce the rate at which heat is emitted by the compressor to its environment and thereby increase the rate at which heat is carried to the condenser and point of use, there exist problems with insulation of the compressor to eliminate significant heat loss therefrom. In fact, arrangements are normally made for heat to escape from the compressor and its driving motor to their environment in order to avoid overheating and inefficient operation of or damage to the compressor and its motor.

In order to make heat lost from the compressor and its driving motor available at the point of use, it has beeen proposed to position the compressor and its motor in close proximity to the condenser.

Thus, it has been proposed to situate the compressor, its motor and the condenser in a common tank containing a secondary fluid.

According to the first aspect of the invention, I provide a heat pump wherein the compressor and/or its motor is or are so associated with the evaporator that heat emitted from the compressor and/or its motor is absorbed by the evaporator and transmitted thereby to the heat transfer fluid.

According to a second aspect of the invention, I provide a method of supplying heat wherein a heat transfer fluid is circulated through a condenser, an evaporator and a compressor, receives heat from a heat source at the evaporator and yields up heat at the condenser and wherein heat emitted by the compressor is transferred to the heat transfer fluid in the evaporator.

In the use of a heat pump, it is generally the case that the higher the rate of heat output and/or the higher the temperature of the condenser and/or the greater the ratio of the rate of heat output to the rate of energy input to the motor, the more useful is the heat pump.

By associating the compressor and/or the motor with the evaporator in accordance with the invention, the temperature of the heat source from which the heat pump extracts heat is raised, as compared with the temperature which would prevail under corresponding conditions in the use of known heat pumps. This results in greater efficiency of the heat pump, a higher rate of heat output from the pump and/or a higher temperature of the condenser.

The arrangement may be such that the evaporator is in direct thermal communication with the compressor. Alternatively, the arrangement may be such that heat is transferred by heat transfer means from the compressor to the evaporator. The heat transfer means may be air or water from which heat is extracted by the heat pump.

One example of a heat pump in accordance with the invention and a manner of use thereof will now be described, with reference to the accompanying drawings which illustrates the heat pump diagrammatically.

The heat pump comprises a cabinet 10 which would typically be situated on the ground floor or basement floor of a house, in a case where the heat pump is to be used for supplying heat to the interior of the house.

In the example illustrated, the heat source is air and an air duct 11 extends through the cabinet to convey air into contact with elements of the heat pump. The air may be extracted from a cavity defined by an outer structure of the house, for example a wall cavity or a cavity between a roof and an upper ceiling of the house. Thus, an air supply duct 12 extends downwardly from a roof space of the house to the duct 11. From a lower end of the duct 11, an exhaust duct 13 leads the exhaust air to the outside of the house.

The heat pump comprises a condenser 14, evaporator 1 5 and compressor 1 6 connected in a closed circuit through which a heat transfer fluid, for example a Freon, circulates. An electric motor for driving the compressor and the compressor itself are contained in a common housing which is mounted in the air duct 11 so that air flowing through the duct can pass on all sides of the compressor. The air duct is preferably cylindrical with its axis coinciding with the axis of rotation of internal rotatable parts of the compressor.

The evaporator 1 5 is a heat exchanger comprising a coil 1 7 of metal tube arranged coaxially with and surrounding the compressor housing. The coil 1 7 and compressor housing are mechanically connected together by vanes 1 8 formed of copper or other material which is a good conductor of heat. The vanes provide a heat flow path for conduction of heat from the compressor to the evaporator coil.

In an alternative arrangement, the compressor 1 6 is spaced along the air duct 11 from the evaporator 1 5 in a direction upstream with respect to the flow of air through the duct. In this alternative arrangement, air flowing through the duct absorbs heat emitted by the compressor and conveys such heat to the evaporator coil.

Above the compressor 16 there is provided in the air duct 11 an electrically driven fan 1 8 for causing air to flow from the roof space down through the supply duct 12, past the compressor 1 6 and evaporator 1 5 and out through the exhaust duct 1 3. For simplicity of illustration, the electrical leads to the motor of the fan 18 and to the motor of the compressor 1 6 are omitted.

However, it will be appreciated that these conductors are not submerged in any liquid but extend through air spaces only so that the arrangement and installation of the conductors is simple, as compared with arrangements of heat pumps wherein electrical conductors necessarily extend through a body of water.

The condenser 14 also is a heat exchanger comprising a coil of copper or other metal pipe.

The condenser coil is submerged in water contained in a tank 1 9 disposed in the cabinet 10 adjacent to the air duct 1 The tank is preferably covered by a thermally insulating layer 20. A flow pipe 21 leads from the interior of the tank to radiators or other heat emitting devices in the house and a return pipe 22 from the heat emitting device leads the return flow of water into the bottom of the tank 19. In the return pipe, there is provided a water-circulating pump 23.

It will be noted that the pipes 24, 25 and 26 of the heat transfer fluid circuit which connect the condenser with the compressor, the compressor with the evaporator and the evaporator with the condenser respectively are short. The volume of heat transfer fluid is correspondingly small. Also, the frictional losses in the heat transfer fluid circuit are small.

Those parts of the heat transfer fluid circuit which contain heat transfer fluid above the ambient temperature during operation can be thermally insulated without difficulty and the parts which are required to be insulated are compact so that the volume of thermal insulation required is relatively small. It will be noted that the electric motors of the fan 1 8 and compressor 16 are disposed in a relatively cool region where the operating conditions are particularly suitable.

These motors run cool and therefore operate with high efficiency.

During operation, the heat transfer fluid evaporates in the coil of the evaporator 15 and absorbs heat. The main source of this heat is the air which flows through the duct 11 but the compressor 16, its motor and the motor of the fan 1 8 are supplementary sources of heat for the evaporator.

The vapour of the heat transfer fluid flows from the evaporator through the compressor to the condenser 1 4 where it yields its latent heat of evaporation to the water in the tank 19. From the condenser, the liquid of the heat transfer fluid flows via a flow-restricting device (not shown) back to the evaporator coil. Water flows from the tank 1 9 to carry heat to the point of use and returns to the tank for re-heating.

Unless the dew point of the air flowing through the air duct 11 is unusually low, ice will be deposited on the evaporator 15. When there has accumulated on the evaporator sufficient ice to interfere significantly with heat transfer between the air and the evaporator, it is necessary to bring about removal of the ice by carrying out a deicing cycle. For this purpose, there is usually associated with the evaporator of a heat pump an electrical heating element whereby the temperature of the evaporator can be raised temporarily. In a de-icing cycle, the compressor is deenergised and the heating element associated with the evaporator is energised, usually for a predetermined period.

Normal operation is then resumed.

With known heat pumps used for extracting heat from air, a control system is provided to initiate de-icing cycles at a predetermined frequency, typically a frequency of one cycle per hour. The flow of heat from the compressor and its driving motor to the evaporator of a heat pump in accordance with the present invention reduces the rate of accumulation of ice on the evaporator, as compared with the rate of accumulation under corresponding conditions in a known heat pump.

Accordingly, the frequency of de-icing cycles in operation of a heat pump in accordance with the invention can be lower than is the case with known heat pumps.

If heat is required at a single point of use, the tank, flow and return pipes 21 and 22 and the pump 23 may be omitted. In this case, the condenser itself operates as a heat supply means at the point of use and emits heat directly by radiation or otherwise.

The source of heat for the heat pump may be a liquid instead of air. For example, the source may be water which has been heated in a solar collector. In this case, the air duct 11 is substituted by a water flow duct connected by flow and return ducts with the solar connector.

Gravity flow of water through these ducts may be adequate, in which case no water pump corresponding to the fan 1 8 would be required.

The water from the solar panel would flow over the evaporator coil. However, the arrangement may be such that the water from the solar collector does not flow over the casing of the compressor 1 6. For conveying heat from the compressor to the evaporator coil, there would then be provided a metal structure to provide a heat flow path adequate to convey to the evaporator coil the heat emitted by the compressor.

Claims

1. A heat pump wherein the compressor and/or its motor is or are so associated with the evaporator that heat emitted from the compressor and/or its motor is absorbed by the evaporator and transmitted thereby to the heat transfer fluid.

2. A method of supplying heat wherein a heat transfer fluid is circulated through a condenser, an evaporator and a compressor, receives heat from a heat source at the evaporator and yields up heat at the condenser and wherein heat emitted by the compressor is transferred to the heat transfer fluid in the evaporator.

3. A heat pump according to Claim 1 wherein the evaporator is in direct thermal communication with the compressor.

4. A method according to Claim 2 wherein heat is transferred by heat transfer means from the compressor to the evaporator.

5. A method according to Claim 4 wherein the heat transfer means is air or water from which heat is extracted by the heat pump.

6. A heat pump substantially as herein described with reference to and as shown in the accompanying drawing.

7. A method of supplying heat substantially as herein described with reference to the accompanying drawing.

8. Any novel feature or novel combination of features disclosed herein or in the accompanying drawing.