WO1990001659A1

WO1990001659A1 - Evaporator plate

Info

Publication number: WO1990001659A1
Application number: PCT/AU1989/000345
Authority: WO
Inventors: Mark George Fleming
Original assignee: Siddons Ramset Limited
Priority date: 1988-08-15
Filing date: 1989-08-15
Publication date: 1990-02-22

Abstract

An evaporator plate (2, 3, 4) suitable for use in a heat pump system, comprising a metallic plate in a substantially vertical orientation and having a refrigerant carrying passage (8) formed therein, said passage (8) including a refrigerant inlet passage (9) opening into a distribution chamber or manifold (11) from which a multiplicity of refrigerant flow passages (13-17) extend and branch into substantially parallel refrigerant flow passages (13a-17b) extending longitudinally of said plate, and a refrigerant outlet passage (10) connected to the ends of said parallel passages (13a-17b) for connection to a compressor, said inlet passage (9) being connected to said manifold (11) at a position (12) which is lower than the refrigerant flow carrying passages (13-17), said manifold (11) being constructed to define a surface down which liquid that separates from the refrigerant may flow back towards the inlet (12) to said manifold (11).

Description

TITLE: EVAPORATOR PLATE

FIELD OF THE INVENTION This invention relates to evaporator plates for heat pump based water heating systems, and to water heating systems employing such evaporator plates.

BACKGROUND OF THE INVENTION In our copending Patent Application AU-A67436/87 , the contents of which are incorporated herein by cross reference, we describe a solar boosted heat pump water heating system based on the invention described in Australian Patent No. 509901, with modifications. While the system described in the above patent application has been found to operate effectively in practice, it has been found that the cost of installation of the roof mounted evaporator plates forms a significant component of the overall cost of the water heating systems. In regions where the net periods of exposed sunlight are relatively low, or where the ambient temperature is relatively high for most of the year, the cost of roof mounting of the evaporator plates may not be warranted . Furthermore, it ould appear that the labour cost of roof mou ting the evaporator plates may more than offset the economic advantage of exposure of the evaporator plates to the sun, except in regions of high net solar exposure.

It has been found that significant cost advantages flow from mounting one or more evaporator panels in surrounding relationship to the water tank of the water heater in a manner which exposes the surface of the evaporator plate to the ambient conditions, since the connections between said evaporator plate and the heat pump compressor may be formed during manufacture of said water heating system thereby avoiding many of the expenses associated with roof mounting. In this way the overall cost of manufacture and installation of the water heating system may be substantially reduced. It has also been predicted that even in regions where the average ambient temperature and the number of days of exposed sun are quite low, the installation cost savings involved in using the above defined arrangement may more than offset the reduced efficiency of a s stem in which the evaporator plates are not

^SUBSTITUTESHEET directly exposed to the sunlight.

All heat pumps carry oil in their refrigerant. For this reason, evaporator plates must be designed in a manner which ensures that the oil is carried through the system to the compressor. In the evaporator plate described in greater detail in our copending application referred to above, the evaporator plate was mounted in an inclined manner, and the oil was able to be drained by gravity and refrigerant flow through the plates. However, since the most convenient orientation for the evaporator plates when carried by the water tanks is vertical and since the evaporator plate design used in the system described in our co- pending application only works effectively when the refrigerant carrying passages extend generally horizontally whereby the serpentine pattern of passages across the plate is able to free drain, the use of this plate design is not practical because the number of U-bends is considerably increased, which in turn increases the pressure drop in the plates to such an e tent that efficient operation is not encouraged. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved evaporator plate or refrigerant flow divider which facilitates the effective operation in a heat pump based water heating system with the evaporator plate mounted substantially vertically, and which offers advantages in other refrigerator and coolroom applications.

The invention therefore provides an evaporator plate or flow divider member comprising means defining a refrigerant carrying passage, said passage including a refrigerant inlet passage opening into a distribution chamber or manifold from which a multiplicity of refrigerant flow passages extend, said manifold being positioned to define a surface down which liquid that separates from the refrigerant may flow back towards the inlet to said manifold.

The fundamental difference between the flow distribution achieved as a result of the manifold arrangement defined above and the presently known systems is that balance is achieved in the known systems by equal pressure drop in the outlet tubes, whereas in the arrangement of the present invention, a balanced mass flo rate and increased dryness fraction is achieved by dispersed flow entering the refrigerant flow passages, or outlet tubes.

In a further aspect, the invention provides an evaporator plate capable of being used in a substantially vertical orientation in a heat pump system, comprising a metallic plate having a refrigerant carrying passage formed therein, said passage including a refrigerant inlet passage opening into a distribution chamber or manifold from which a multiplicity of refrigerant flow passages extend and branch into substantially parallel refrigerant flow- passages extending along the plate, and a refrigerant outlet passage connected to the ends of^" said parallel passages for connection to a compressor, said inlet passage being connected to said manifold at a position which is lower than the refrigerant flow passages connected to said manifold, said manifold being constructed to define a surface down which liquid that separates from the refrigerant may flow back towards the inlet to said manifold .

In a preferred form of the invention, the manifold is arranged at a negative acute angle of inclination to the longitudinal axis of the plate. The inlet to the manifold preferably includes a restricted inlet orifice which causes the liquid and vapour entering the manifold to be in a dispersed flow, which passes up into the manifold so that the manifold contains a uniform dispersed mixture of liquid and vapour which is drawn off by the outlet passages from the manifold. By virtue of the inclined arrangement of the manifold, any liquid which separates from the dispersed mixture runs down the backside of the manifold where it re-enters the inlet jet from the inlet orifice and is redispersed. The refrigerant passages from the manifold to the parallel passages are also formed with a restriction orifice which is dimensioned to balance the mass flow rate in each refrigerant passage.

In a particularly preferred form of the invention, each refrigerant passage from the manifold is preferably divided into two parallel passages and the restriction orifice is preferabl formed just before the branching of the passage to more evenly

SUBSTITUTESHEET divide the flow of refrigerant into each branch.

While the above defined evaporator plate is capable of being used in a vertical orientation, thereby overcoming the inadequacies of the evaporator plate designed for slightly inclined use, the plate will operate with equal efficiency in any other orientation, and may therefore be used in a roof mounted system, such as that described in greater detail in our copending patent application referred to above.

The evaporator plate defined above is not limited to use in heat pump systems and may also be used as a refrigeration evaporator.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred form of each of the above aspects will now be described with reference to the accompanying drawings in which:

Figure 1 is a front elevation of a water heating system embodying the present invention utilising the evaporator plate according to the present invention;

Figure 2 is a fragmentary end view of the system of Fig. 1 showing the attachment of the evaporator plates to the water tank: Figure 3 is a front perspective view of an evaporator plate embodying the invention;

Figure 4 is a detailed view of the inlet end of the evaporator plate of Fig. 3 and

Figure 5 is a detailed view of the outlet end of the plate of Fig. 3:

Referring firstly to Figs. 1 and 2 of the drawings, the water heating system embodying the present invention comprises a water tank (not visible), a refrigerant carrying coil (not visible) surrounding the lower portion of the tank, insulating material (not visible) covering the tank and the coil and enclosed within an outer casing 1. A compressor (not visible) is supported on top of the tank within the casing 1, the arrangement thus far described being substantially identical to the water heater described in our copending Patent Application AU-A67436/S7. The principal difference between the water heater of the present invention and the water heater described in the copending patent application is that the evaporator plates 2, 3 and 4 are shaped to surround the outer casing 1 and are attached in position around the casing 1 by means of saddle brackets 5 attached to the casing 1 in the manner shown in Fig. 2 of the drawings. The evaporator plate 2, 3 and 4 are formed with an angular flange 7 by means of which the plates are secured to the saddle brackets 5 and to each other. These flanges 7 also serve to give the plates 2, 3 and 4 additional rigidity.

Each evaporator plate 2, 3 and 4 is formed by the Rollbond process with refrigerant carrying passages 8 which will be described in greater detail below. The refrigerant carrying passages 8 include an inlet passage 9 and an outlet passage 10 (Fig. 3), which are connected by suitable fittings (not visible) to the remainder of the heat pump which includes the condenser, so that refrigerant fluid enters at the top of the plate and circulates through the passages 8 and exits through the outlet passage 10.

Referring no to Figs. 3 to 5 of the dra ings, the configuration of the passages 8 in the evaporator plate embodying the invention will no be described in greater detail. It will be noted from Figs. 3 and 4 that the inlet passage enters the low end of a distribution chamber or manifold 11 which is inclined towards the left edge of the plate at an angle of about 45 to the horizontal. At the point at which the inlet passage 9 enters the manifold 11, the passage is formed with an inlet orifice 12 (Fig. 4) which is dimensioned to cause the liquid and vapour refrigeran which enters the manifold to be in a dispersed flow. A multiplicity of refrigerant transfer passages 13, 14, 15, 16 and 17 open into the manifold 11, and the inclination of the manifold 11 causes any liquid which separates from the dispersed mixture to run down the backside of the manifold in the direction of the arrow 23 in Fig. 4 of the drawings, where the liquid re-enters the inlet jet from the inlet orifice 12 and is re-dispersed into the manifold 11.

The liquid and vapour in the manifold 11 is drawn off through the transfer passages 13 to 17 where it proceeds down the transfer passage to a point where each transfer passages enters a pair of parallel paths 13a, 13b, 14a. 14b, 15a, 15b, 16a, 16b and 17a, 17b.

_SUBSTITUTESHEET At the point of divergence, each transfer passage 13 to 17 is formed with a further restricting orifice which is dimensioned to ensure that the flow of refrigerant in the divided passages is substantially even.

At the lower end of the plate, the parallel passages 13a to 17b open into a collection passage 18 which is inclined to the horizontal at an angle of about 10°. The passage 18 is formed with an oil trap 19 at its lowermost point, the uppermost portion of the trap being connected to the outlet passage 10 which proceeds from the trap 19 to the uppermost edge of the plate.

In one commercial embodiment, successful results have been achieved with inlet and outlet passages about 8 mm in diameter, a manifold passage about 10 mm in diameter, transfer passages about 6 mm in diameter, parallel passages about 402 mm in diameter and restricting orifices about 3.5 mm in diameter. However, these dimensions of the passages, orifices and manifold are exemplary only and should not be taken as limiting the invention in any way.

While the preferred evaporator plate described above is particularly suited for use in a vertical orientation, as shown in Fig. 1 of the drawings, the plate is equally effective in operation in the manner described in our copending patent application referred to above. Similarly, although the preferred evaporation plate is made by the Roll Bond process, the passages may be machined or cast in any suitable material.

The claims form part of the disclosure of the specification.

Claims

CLAIMS :

1. An evaporator plate or flow divider (2, 3, 4) comprising means (8) defining a refrigerant carrying passage, said passage (8) including a refrigerant inlet passage (9) opening into a distribution chamber or manifold (11) from which a multiplicity of refrigerant flow passages (13, 14, 15) extend, said manifold (11) being positioned to define a surface down which liquid that separates from the refrigerant may flow back towards an inlet (12) to said manifold (11).

2. The evaporator plate or flow divider of claim 1, wherein said manifold (11) is arranged at a negative acute angle of inclination to the longitudinal axis of the plate.

3. The evaporator plate or flow divider of claim 1 or 2, wherein said inlet (12) to said manifold (11) includes a restricted inlet orifice which causes the liquid and vapour entering the manifold (11) to be in a dispersed flow which passes up into said manifold (11) so that said manifold (11) contains a uniform dispersed mixture of liquid and vapour which is drawn off by said outlet passages (13 - 17).

4. The evaporator plate or flow divider of claim 3, wherein said outlet passages (13 - 17) from said manifold (11) are connected to parallel refrigerant passages (13a, 13b to 17a, 17) via restriction orifices (13c - 17c) dimensioned to balance the mass flow rate in each parallel passage.

5. In a heat pump system, an evaporator plate (2, 3, ) capable of being used in a substantially vertical orientation and comprising a metallic plate having a refrigerant carrying passage (8) formed therein, said passage (8) including a refrigerant inlet passage (9) opening into a distribution chamber or manifold (11) from which a multiplicity of refrigerant flow passages (13 - 17) extend and branch into substantially parallel refrigerant flow- passages (13a - 17b) extending longitudinally of said plate, and a refrigerant outlet passage (10) connected to the ends of said parallel passages (13a - 17b) for connection to a compressor, said inlet passage (9) being connected to said manifold (11) at a position (12) which is lower than the refrigerant flow carrying

_SUBST_ITU_TESHEET passages (13 - 17), said manifold (11) being constructed to define a surface down which liquid that separates from the refrigerant may flow back towards the inlet (12) to said manifold (11).

6. The evaporator plate of claim 5, wherein said manifold II is arranged at a negative acute angle of inclination to the longitudinal axis of the plate.

7. The evaporator plate or flow divider of claim 6, wherein said inlet (12) to said manifold (11) includes a restricted inlet orifice which causes the liquid and vapour entering the manifold (11) to be in a dispersed flow which passes up into said manifold (11) so that said manifold (11) contains a uniform dispersed mixture of liquid and vapour which is drawn off by said outlet passages (13 - 17).

SUBSTITUTESHEET