GB2504913A

GB2504913A - Heat recovery system

Info

Publication number: GB2504913A
Application number: GB1111277.8A
Authority: GB
Inventors: Charles Madondo
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-07-01
Filing date: 2011-07-01
Publication date: 2014-02-19
Also published as: GB201111277D0

Abstract

A heat recovery system of waste water from a domestic, industrial or commercial property comprises a heat exchanger 2A, 2B arranged to absorb heat from heated waste water and transfer the heat to water cooler than the heated waste water. The transfer of heat could be increased via a refrigeration circuit comprising a first heat exchanger 2B (evaporator) whereby the heated waste water vaporises a coolant (refrigerant) and is communicated via a compressor 2C to a second heat exchanger 2A (condenser) that heats water that is to be supplied to water storage tank 3 for use at a later stage. The cooled condensed coolant leaving the second heat exchanger returns to the first heat exchanger via an expansion valve 2D. To prevent blockages of the heat exchanger a backwash cleaning system may be used to remove fouling. A pressure gauge (8, fig 1) may be used to trigger when cleaning is required and cleaning chemicals in a tank 4 may be used to increase cleaning. A temperature control unit 9 may regulate flow of heated water to the water storage tank, which may be used as boiler feed water.

Description

Waste heat controller This invention relates to a device for recovering heat energy lost through drainage from a household, industrial or commercial property.

When hot water is used in a building for various purposes, like bathing, shower, washer or sink or any other industrial process, this water finds its way to drain sometimes at temperatures as high as degrees or more. This results in wastage of heat which could have otherwise been used for other purposes before being lost to drain.

Used up water is lost to drain at various stages at different temperatures and quantities and at different times of the day. This then relates to the cost of heating through gas or electricity, where a gas boiler or a heating coil raises the cold water temperature from average 10 degrees Celsius to an average boiler delivery temperature of 52 degrees Celsius or more. To overcome this, the present invention proposes a waste heat controller that will strip off as much heat from the warm water before it goes to drain and this being achieved by mounting a heat exchange unit (figurel & 2)) and alternatively using a multiphase heat retention unit (figure 3 & 4) that incorporates a compressor and a coolant. The use of the waste heat controller will result in the reduction of the amount of gas or electricity needed in generation of heat energy for water. Preferably the units should be fitted with a backwash unit that will address issues of blockage and fouling.

The first heat retention unit used will be a flat waste heat exchanger with warm water flowing in the tube side counter current cold water in the shell side. A flat heat exchanger (figure 1 & 2) is proposed as it does not take much space and is also easy to install. Other variations can be used to promote effective heat transfer e.g. plate heat exchanger, depending on the quantities of drainage water.

The second heat retention unit used will be a multiphase heat exchange unit (figure 1 & 2) coupled to a compressor circulating a coolant. The unit will be a double shell and tube heat exchanger warming up the coolant in the first stage from warm drain water and losing the heat to cold water in the second stage and thereby raising the temperature of boiler feed water or electrical heating tank feed water. Other exchanger types can be used to suit the requirements.

The invention can now be described by way of example and with reference to the accompanying drawings.

Figure 1 shows a flat type waste heat exchanger installed on the drain water outlet viewed from the top.

Figure 2 shows the flat waste heat controller fitted to the drain water outlet with its backwashing system from a perspective view.

Figure 3 shows the multiphase heat exchanger with its compression and coolant pipe work viewed from the top.

Figure 4 shows the multiphase heat exchanger with its compression and coolant pipe work from a perspective view.

In figure 1, a heat exchanger (flat type) 2, is installed on the drain outlet 6, and also connects to the cold water supply 1. The drain water enters the exchanger and flows through the tubes, while the cold water enters the heat exchanger 2, through the shell side. A counter current flow is established and in this way heat is passed on from the higher temperature medium to the lower temperature medium. Warm feed water comes out of the heat exchanger and passes through a temperature control unit 9, which regulates flow according to set temperature value before being allowed into a storage tank 3. The warm water storage tank can store water at that set temperature for up to 24 hours or more. This water is then used by the boiler as boiler feed water or as feed water to the electrical heating tank.

In figure 2 the waste heat controller is supported by function of the differential pressure gauge 8, which triggers off backwashing of the unit through backwashing outlet 5. The waste heat exchanger will encounter dirty water which is frothy, filthy, soapy, muddy, and any other which might cause blockage across the unit. This type of fouling may result in poor function of the unit. To overcome that, a backwash cycle can be employed as and when required through the sensing of a differential pressure gaugeS. To initiate a backwash cycle, a number of valves have to be operated manually or automatically. This cycle will temporarily stop the function of the heat exchanger, but a suitable time can be selected to initiate the cycle. To increase the effectiveness of the backwash, a chemical tank 4 is attached to the system in such a manner that it will dose the required chemicals during a backwash cycle. The chemicals are mainly to remove severe blockage and dislodge scaling.

Figure 3 shows a further modification of the waste heat controller in which the flat exchanger, is replaced by double cylindrical shell and tube heat exchangers that are interconnected by a compressor driving a coolant between the two exchangers 2A and 2B. The liquid coolant in exchanger 2B is vaporised as and when warm water to drain 6, passes through the exchanger 2B.

The compressor 2C pressurises the gas and pushes the gas into exchanger 2A where it will be cooled by cold water in the tube side. The cold water picks up heat in the exchanger 2A and the gas liquefies and enters the exchanger 2B via an expansion valve. More rapid heating and cooling is experienced and thereby increasing the efficiency of the unit. Backwashing is achieved in the same manner as in figure 1.

Figure 4 shows a perspective view of the multiphase heat exchanger. Cold water enters the system through 1. Heat exchanger 2A passes any heat to the cold water through the circulating gas. Warm water to drain 6, enters the heat exchanger 2B and gives off any heat to the liquefied coolant in 2B.

Drain water continues out via pipe 7, to drain. Backwashing can be initiated by reversing flow of cold water through exchanger 2B and allowing any debris to come out through pipe work 5. A number of valves have to be operated manually or automatically to start the backwash cycle. The chemical tank 4, can store selected chemicals that help remove blockages and scaling.

Claims

Claims 1 A waste heat controller that will strip off as much heat from the warm water before it goes to drain and this being achieved by mounting a heat exchanger and alternatively using a multiphase heat retention unit that can incorporate a compressor and a coolant to increase effectiveness.
2 A waste heat controller according to claim 1 that retains heat from drain water and uses that heat to raise the boiler feed water temperature or the temperature of the water at the heating point thereby reducing the amount of energy used in heating water.
3 A waste heat controller according to claim 1, in which the heat exchanger unit is fitted with a backwash unit to remove fouling and blockage and a differential pressure gauge to sense blockage.
4 A waste heat controller according to claim 2 that has a chemical dose tank fitted on stream to inject selected chemicals that help remove blockages and scaling.A waste heat controller according to any of the preceding claims, in which a temperature control valve is fitted on the outlet of the exchanger to ensure the set value temperature of warm water, enters the storage tank.