Chilled Water Cooling Coil Design

Methods to design the cooling and dehumidifying coil either chilled water coil or dx evaporator coil are usually based on log mean enthalpy or log equivalent dry bulb temperature difference.

Chilled water cooling coil design.

Chilled water cooling coil selection example 4 chilled water coil worksheet example 5 chilled water coil worksheet 6 enthalpy of air table 1 7 air density correction at altitude table 2 7 air density correction at temperature table 3 7 log mean temperature difference table 4 8 basic capacity figure 1 8fpi 9 basic capacity figure 2 1ofpi 10. Designated by the fluids in the tube. Properly protect water coils from freezing when necessary agenda water and air velocity ranges coil selection examples chilled. Designing and operating chillers at low temperatures increases the chiller lift and reduces the efficiency of the chiller.

Evaluate water coil selection choices at various water temperatures and flow rates 4. Chilled water coils are one of the most common mediums for cooling air. If the flow rate in the secondary side is low then some chilled water will flow into the secondary and some will recirculate back to the chillers. Understand the balance of coil face area airside pressure drop and waterside pressure drop when selecting a coil 5.

In both methods the cooling coil is treated as a single zone region and hence the required surface area is determined. There is really no difference between hot water coils and a chilled water coils in construction. For a given design load the chiller is selected for fixed temperature range t and the associated chilled water pumps are selected for calculated flow rate. The vast majority of chilled water coils are constructed from either 1 2 od tubes or 5 8 od tubes.

So a chilled water coil is a fin and tube heat exchanger used for cooling air where the coolant is chilled water and the direct expansion coil is a fin and tube evaporator found in a vapour compression cycle. Beginning in its 2016 version ashrae standard 90 1 now requires chilled water cooling coils be designed for at least a 15 f temperature difference δt between the leaving and entering water. And the leaving water temperature must be no colder than 57 f at design conditions 1. The chilled water supply temperature usually has a fixed set point and the only variable that affects the output capacity of chiller is the return water temperature.

The chilled water is generated and circulated in the primary side the secondary loops will pull chilled water out of the header to cool the building and then dump the warm return back into the header.