Gas and liquid contact apparatus – With external supply or removal of heat – Heat exchange means at or downstream of contact zone
Patent
1997-06-25
1999-07-06
Woo, Jay H.
Gas and liquid contact apparatus
With external supply or removal of heat
Heat exchange means at or downstream of contact zone
261111, 261116, 1341033, 165166, B01D 4700
Patent
active
059194065
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a process for cooling and cleaning the planar elements of a plate heat exchanger to recover extraction air heat by spraying water into an extraction air flow. The invention also concerns a wetting device for performance of the process.
In the air conditioning of residential, working and storage areas and temperature-sensitive objects, depending on the sensitivity level, heating and/or cooling for heating but also for cooling, the recycling principle has begun to apply in view of the ever tightening ecological constraints combined with rising energy costs. The extracted air, depending on the season, is used to pre-cool or pre-heat the outside air. To achieve maximum efficiency, the two air flows are passed through each other, strictly separated and with a maximum exchange surface area. The plate heat exchangers frequently used for this work on the backflow principle or preferably the cross-flow principle.
A plate heat exchanger for ventilation systems is described for example in EP, A2 0449783. This heat exchanger consists of planar elements of similar form stacked onto each other and spaced apart by means of inserted or moulded spacers. This cross-flow heat exchanger, thanks to the thin planar elements and the intermediate spaces which are usually only 0.2-1.5 cm wide, allows an efficient transfer of heat between the two crossing air flows. The plates, for example 0.1-0.5 mm thick, preferably consist of a good heat conductive metal such as aluminium or steel but also of mechanically strong plastic or a composite material.
It is known to improve the cooling of the external air passed through a plate heat exchanger by the effect of tap water nozzles. Spraying takes place preferably onto the extraction air inlet side. A spray cone is aimed at the planar elements, the spray water drips onto the outlet side of the extraction air, is caught and usually pumped back into a circuit system. Heat convection and partial evaporation of the water cools the planar elements. Heat can be extracted from the external air flow crossing on the other side of the planar element without influencing its moisture balance.
FIG. 1 shows a diagrammatic view of a known plate heat exchanger 10 with vertically arranged parallel planar elements which comprise two blocks 12, 14. The extraction air flow 16 passes firstly through block 12 then through block 14 from which it emerges as continuation air flow 18. On the inlet side of the extraction air flow 16 is arranged a nozzle rail 24 with three nozzles, not shown for the sake of simplicity, each of which sprays a spray cone 26 into the inlet slot of element 12. On a further opposite nozzle rail 28 are arranged three nozzles in the area of element 12 spraying against the air flow and three nozzles in the area of element 14 spraying in the direction of the air flow. The water 30, permanently sprayed with considerable surplus into the plate heat exchanger 10, drips into a catchment trough 32. With a pipe or hose system not shown, the water 30 can be pumped back into the fixed mounted nozzle rails 24, 28, after cleaning where applicable, or passed to the waste water system. This cooling system requires a large quantity of tap water and is costly to operate.
FIG. 2 shows diagrammatically a cooling system which comprises a plate heat exchanger 10 with a single block. The extraction air flow 16 guided from a room 34 is passed through a moisturising system 36 with several spray cones 26. The moistened extraction air flow 16 is cooled for example from 25 to 19.degree. C. As the external air flow 20 crossing in the heat exchanger 10 is warmer, the planar elements in the exchanger remain dry.
The purpose of the invention is to create a process and a device of the type described above in which the efficiency of the cooling water used is increased. The plate heat exchanger can also be cleaned with the same device.
In relation to the process, a task is solved according to the invention in that by means of wetting nozzles a fine spray jet of treated water is sprayed upstream at equ
REFERENCES:
patent: 2825210 (1958-03-01), Carr
patent: 3156547 (1964-11-01), Fleck
patent: 4477483 (1984-10-01), Lewis
Hopkins Robert
Polybloc AG
Woo Jay H.
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