GB2113367A

GB2113367A - Water-heating apparatus

Info

Publication number: GB2113367A
Application number: GB08300568A
Authority: GB
Inventors: Albertus Peter Johanne Michels; Franco Moretti
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1982-01-14
Filing date: 1983-01-10
Publication date: 1983-08-03
Also published as: GB2113367B; GB8300568D0; JPS58130926A; DE3300339A1; FR2519743A1; IT8220465V0

Abstract

A water-heating apparatus comprises a thermally insulated water container (1) with a cold-water inlet (6) and a hot-water outlet (7), and a heat pump for heating the water in the container. The heat pump comprises a condenser (10) arranged for heat exchange with the water in the container, an evaporator (14) and a motor-compressor unit (8) for circulating the fluid heat-transporting medium in the heat pump and also compressing it. To inhibit or reduce condensation of the evaporated heat-transporting medium in the motor-compressor unit, and the resulting contamination of the lubricant therein, when this unit, which is controlled by a thermostat, is stopped, the motor-compressor unit is mounted on top of the water container and means are provided whereby heat can be transferred to the unit from the heated water in the container. These means may comprise an opening (20) in the insulation (4) of the container directly beneath the motor-compressor unit, a heat pipe or a metal heat conductor extending through the insulation. <IMAGE>

Description

SPECIFICATION Water-heating apparatus The invention relates to a water-heating apparatus comprising a thermally insulated water container with an inlet for cold water and an outlet for heated water, and a heat pump comprising a condenser which is arranged for heat exchange with the water in the container and a motor-compressor unit which is arranged externally of the container for circulating a fluid heat-transporting medium in the heat pump.

The condenser may form an integral part of the container but this is not essential. An apparatus of this type is described in, for example, the Applicants' Italian Patent Application No. 27609 A/78 dated 13.9.1978.

The motor-compressor unit may be enclosed in a metal casing or capsule which forms a chamber into which flows the heat-transporting medium circulating in the heat pump and which is connected to the suction side of the motor-compressor unit.

In known apparatus for producing hot water by means of a heat pump, it has been found that the motor-compressor unit is inadequately lubricated when brought into operation after a prolonged stoppage, with the result that the unit may seize up and in any case suffer a reduction in its working life. This drawback is due to the fact that during periods when the motor-compressor unit is not in operation, heat-transporting medium condenses in the capsule of the unit due to the inevitable cooling, and this condensate mixes with the lubricating oil present in the capsule to cause its lubricating characteristics to deteriorate to an extent which increases as the quantity of mixed condensate increases.

It is an object of the invention to mitigate this drawback.

According to the invention there is provided a water-heating apparatus comprising a thermally-insulated water container with an inlet for cold water and an outlet for heated water, and a heat pump comprising a condenser which is arranged for heat exchange with the water in the container and a motor-compressor unit which is arranged externally of the container for circulating a fluid heat-transporting medium in the heat pump, wherein the motor-compressor unit is disposed on the top of the container and means are provided whereby heat can be transferred to said unit from the heated water in the container.

The heat transferred to the motor-compressor unit causes at least partial evaporation of heat-transporting medium which condenses in the unit when it is not in operation, with consequent improvement in the lubricating conditions.

In one embodiment of the invention the container comprises a metal shell enclosed in a thermally insulating jacket, and the means whereby heat can be transferred to the motorcompressor unit comprise an opening in the insulating jacket through which heat can pass to the motor-compressor unit from said metal shell.

In another embodiment the means whereby heat can ba transferred to the motor-compressor unit comprise a heat pipe.

In yet another embodiment the container comprises a metal shell enciosed in a thermally insulating jacket, and the means whereby heat can be transferred to the motorcompressor unit comprise a thermally conductive metal bridge extending through the insulating jacket and attached at one end to the motor-compressor unit and at the other end to said metal shell.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which Figs. 1, 2 and 3 are diagrammatic representations of three embodiments of the apparatus according to the invention with the water container shown in sectional elevation, each embodiment comprising a different means for the transference of heat from the heated water in the water container to the motor-compressor unit.

In each embodiment the water container, designated 1, comprises an inner metal shell 2 defining a water-containing compartment 3 a thermally insulating jacket 4 enclosing the shell 2, and an optional outer metal shell 5. A cold-water feed pipe 6 opens into the bottom of the compartment 3, and a hot-water outlet pipe 7 extends up through the bottom of the container 1 and terminates in the upper part of the compartment 3. Alternatively, a direct outlet for hot water may be provided in the top of the compartment 3.

The apparatus further comprises a heat pump for heating the water in the container 1. In each of the embodiments shown the heat pump comprises an encapsulated motorcompressor unit 8 arranged outside the container 1 for circulating a fluid heat-transporting medium in the heat pump and also compressing this medium, a pipe 9 leading from the motor-compressor unit 8 to a condenser 10 which is arranged in the lower part of the container 3 for heat exchange with the water contained in this part of the compartment, a pipe 1 leading from the condenser 10, via a filter 1 2 and an expansion valve 13, to an evaporator 1 4 for absorbing heat from the surrounding atmosphere (external to the compartment 3), and a return pipe 1 5 which returns the heat-transporting medium to the encapsulated motor-compressor unit 8 for recirculation thereby.

During the construction of the apparatus, a certain quantity of oil is introduced into the heat pump, specifically, into the capsule of the motor-compressor unit, for lubricating the moving parts of this unit.

A thermostat, not shown, controls the operation of the motor-compressor unit 8 in accordance with the water temperature in the upper part of the compartment 3, in known manner.

Without the means provided by the present invention, during the periods when the motorcompressore unit is not in operation, which periods could iast for some hours in an apparatus of this type, evaporated heat-transporting medium would condense in the motorcompressor unit, specifically, in the capsule containing it, due to the natural cooling to which the vapour is subjected, and the condensed medium would mix with the oil, thereby impairing its lubricating characteristics to an extent which increases as the quantity of condensate increases. The consequence of this would be that when the motor-compressor unit is started again it would be inadequately lubricated and could consequently seize up. The increased wear of the moving parts of the unit would in any case appreciably reduce its working life.

The invention mitigates this problem by providing for a small quantity of heat to be transferred from the heated water in the compartment 3 to the motor-compressor unit when the latter is not in operation, so as to at least reduce, by virtue of consequent evaporation, the quantity of condensed heat-transporting medium available to mix with the lubricating oil in the motor-compressor unit.

The heat can be transferred in various ways, all requiring the motor-compressor unit 8 to be disposed on the top of the container 1, for example, on the outer shell 5 of the container, as shown in the drawings. In the embodiment shown in Fig. 1 the motor-compressor unit is mounted directly over an opening 20 in the insulating jacket 4 and outer shell 5, through which opening heat can pass to the motor-compressor unit 8 by radiation and convection from the exposed portion 21 of the inner shell 2, which portion is in direct contact with the heated water in the top of the compartment 3.

In the embodiment shown in Fig. 2 a heat pipe 22 is used for the transference of heat from the heated water in the upper part of the compartment 3 to the motor-compressor unit 8. As is well known, a heat pipe is a device which transports heat by evaporation and condensation of a fluid medium in a closed, usually elongate, container. The medium evaporated in a heated region of the container, flows in the vapour phase to a region of lower temperature as a result of the lower vapour pressure prevailing there, and condenses in the latter region while giving up its latent heat through the wall of the container at this region. The condensed medium returns to the heated region of the container either under the influence of gravity or, if the disposition of the container does not permit this, through capillary means provided on the walls of the container. The heat pipe 22 in Fig. 2 has one end portion arranged in contact with the inner shell 2 of the container 1 to be heated thereby and the other end portion arranged in contact with or extending into the capsule of the motor-compressor unit 8 to give up heat thereto.

In the embodiment of the invention shown in Fig. 3 a bridge 23 made of a metal of good thermal conductivity passes through the insulating jacket 4 and is fixed at one end to the inner shell 2 of the container 1 and at the other end to the capsule of the motor-compressor unit 8.

Claims

1. A water-heating apparatus comprising a thermally-insulated water container with an inlet for cold water and an outlet for heated water, and a heat pump comprising a condenser which is arranged for heat exchange with the water in the container and a motor-compressor unit which is arranged externally of the container for circulating a fluid heat-transporting medium in the heat pump, wherein the motor-compressor unit is disposed on the top of the container and means are provided whereby heat can be transferred to said unit from the heated water in the container.

2. A water-heating apparatus as claimed in Claim 1, wherein the container comprises a metal shell enclosed in a thermally insulating jacket, and wherein the means whereby heat can be transferred to the motor-compressor unit comprise an opening in the insulating jacket through which heat can pass to the motor-compressor unit from said metal shell.

3. A water-heating apparatus as claimed in Claim 1, wherein the means whereby heat can be transferred to the motor-compressor unit comprise a heat pipe.

4. A water-heating apparatus as claimed in Claim 1, wherein the container comprises a metal shell enclosed in a thermally insulting jacket, and wherein the means whereby heat can be transferred to the motor-compressor unit comprise a thermally conductive metal bridge extending through the insulating jacket and attached at one end to the motor-compressor unit and at the other end to said metal shell.

5. A water-heating apparatus substantially as herein described with reference to Fig. 1, 2 or 3 of the accompanying drawings.