Chiller Evaporators
by diywealth on May.25, 2009, under diy
The chillers evaporator is a heat exchanger that transfers heat from a process or air conditioning water circuit to the chillers cooler liquid refrigerant. Most air cooled chillers in the UK chiller hire market will be fitted with a shell and tube evaporator, a plate heat exchanger evaporator or a coil in tank evaporator. A shell and tube evaporator is used primarily on chilled water applications. When a chiller is fitted with this type of evaporator the chillers cool liquid refrigerant flows through tubes encased in a shell.
The process or air conditioning circuit water fills the shell flowing around the tubes. As heat is transferred from the water to the chillers refrigerant the gas boils inside the tubes and the resulting vapour is drawn into the chillers compressor.
Hot water will enter the shell at one end, chilled water leaving at the opposite end.
A Plate heat exchanger evaporator can be used for chilled water or fluid cooling applications. Stainless steel evaporators are especially suited in food and beverage applications such as batch cooling or potable water systems.
A coil in tank evaporator comprises a coil block, usually copper, with aluminium fins to provide an efficient heat transfer surface. The coil block is then submerged in a chilled water tank which acts as a thermal buffer for the refrigeration system. This type of coil is suited to hire chillers used on process cooling applications, typically reactor cooling systems in chemical cooling, petrochemical cooling & pharmaceutical cooling systems.
Air Cooled Chiller Condensers
The condenser is a major component of a water chiller. The condenser is a heat exchanger that rejects heat from the chillers refrigerant to air. Some chillers are water cooled. A Water cooled chiller gives up its heat into relatively cool water from a cooling tower, air-blast cooler or adiabatic cooler. A typical air cooled condenser fitted to an air cooled water chiller will use axial fans (propeller type) to draw outdoor air over a finned tube heat transfer surface (heat exchanger).
The temperature difference or “delta T” between the hot refrigerant gas that is flowing through the condenser and the cooler outdoor air induces heat transfer. The heat reduction of the chillers refrigerant vapour causes it to condense into liquid. The last part of the chiller condenser is called a sub-cooler. The chiller sub-cooler reduces the liquid gas temperature still further, under its condensing temperature. The air cooled chiller is best suited to chiller hire applications. Chiller hire projects require systems to be delivered and installed quickly with the minimum of fuss.
