The difference between the cooler coils and air washers
Evaporative cooling air by adiabatic saturation can be improved by lowering the temperature of feed water, but little improvement in results, if all of feed water evaporates. The picture changes, however, if the speed of injection feed water increases, so not all of it evaporates, but some gets into a sump and is recirculated. When the water flow rate accelerates its temperature was having an increasingly important influence on heat transfer from the airstream. For example, if an arbitrarily large amount of water, were sent at a temperature fw, then the air will leave the spray chamber at fw, in the saturated state.
In the air washing machine, used for cooling and drying processes, the amount of water distributed very large compared to the amount that can be completely evaporated. Water temperature, thus playing an important role in determining the state of the air leaving the washer. On Fig. 10.1 shows the psychrometric considerations.
Direct cooling of this kind is not necessarily the most effective method.
However reversible heat transfer, or even a reasonable approximation to it, cannot be readily obtained in the air washer. On the other hand, when the cooling water circulating through the cooler coil over three rows good measure reversing implemented. This allows a closer approach between the leaving and the temperature at the inlet water temperature cooler with coils using chilled water or in brine. In comparison with the cooler coil washer suffers from a number of disadvantages:
- It is more cumbersome.
- Corrosion is a big risk.
- Maintenance is more expensive.
- He uses outdoor cooling water circuit, thus causing scale, rust, mucus, and others in the water cooler (evaporator), decreasing the efficiency of heat transfer and increasing the cost of refrigeration.
- Micro-organisms tend to establish colonies in the circulating water tank. They may represent a health risk in the case of transportation on the airstream in the conditioned space. Pickering and Jones (1986) discuss how allergic reaction (humidifier fever) may be caused, in some impressionable people who develop symptoms similar to those of mild flu at the beginning of the working week. Immunity acquired by mid-week, but lost over the weekend. The cycle can be repeated.
Humidification by the introduction of dry steam in the right place in the system much better than using air filter. It's fruitless, if not wet and perfectly safe.
There is one point strongly in favor of air washers and sprayed cooler coil: the presence of a large mass of water in the tank and spray chamber gives the thermal inertia of the system, smoothing out fluctuations in the air at the outlet of the coil or plate, and adding stability of functioning of automatic controls. However, despite these positive aspects, air filter, very much out of fashion, because cooler coil is more effectively, and because of the five points mentioned...
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