2. INSTANTANEOUS TYPE WATER COOLERS:
In general the instantaneous type of water coolers consists of two separate cylindrically wound coils. One coil is for the refrigerant and the other for water. They may be made of copper or stainless steel tubes. Usually both the coils are entwined and bonded together by soldering. The water is cooled by the refrigerant by conduction in the evaporator.
The instantaneous type coolers may be further classified as:
- Bottle type,
- Pressure type, and
- Self-contained remote type.
The water that is to be cooled will be stored in a bottle or reservoir. These are usually 25 liters bottles placed on top of the unit. A faucet is used to minimize the wastage of water. The drip receptor receives water that is not used and sends it to the drainage. When we operate the faucet, the water flows from bottle to the water coil through flow regulator. Now as the water travels through the coil, it loses its latent heat to the refrigerant in the evaporator coil there by reduction in water temperature is achieved. A thermostat is placed at the end of the water coil to the compressor start and stop according to the water temperature. This type of cooler may be used in hospitals, shops, home, etc. (The water cooler illustrated at left also provides heated water.)
In this type of cooler, water is supplied under pressure. The city water enters the cooler at the rear of the cooler. It is cooled initially in a pre-cooler. The waste water passing through the drainage line is also cool; hence this drainage pipe is wrapped around the fresh water pipe for pre-cooling thus reducing the cooling load for the cooler. The pre-cooled water is then taken to the storage chamber, where the refrigerant gains heat from the water. The outlet for water is taken from the bottom of the storage tank which may be a bubbler or a self-closing valve. A thermostat is used to control the temperature of water in the pipe to maintain a particular set point.
SELF-CONTAINED REMOTE TYPE:
This system consists of a mechanical refrigeration system, the water being cooled by the cooler which is remote from the desired drinking place. This remote cooler supplies cold water to the desired drinking place.
The thermostat is clamped onto water pipe at its outlet in an instantaneous type water cooler. The flow rate must be adjusted to match its capacity. If rate of flow is more, the cooler will not bring down the temperature of water to the set point and also it results in high evaporator temperature which in turn leads to high suction pressure of the compressor which may adversely affect the compressor motor.