Chilled Water Coil Selection

- Mar 14, 2018-

How to select a chilled water coil?

In the central air handling units or modular air conditioning units, the user can choose a variety of structural parameters of coil, perhaps at the same time there are several kinds of coil can meet the requirements of process air.Therefore, when choosing the structure parameters of coil air handling requirements should be considered, the cost of the coil, a variety of factors such as system operation and management cost, balance the pros and cons, can choose relatively the most suitable for the most economical solution. 

In coil structure parameters influence on cost from big to small in turn is: windward area, row number, distance, loop.The following is from these four aspects to discuss.

1. The windward area of

We generally through the required air volume air conditioning system and flows through the coil head on wind speed to determine aweather area of the coil.For an air conditioning system, air volume have been confirmed, we just choose the right wind speed.We already know from the previous statistical curve, with the increase of wind speed, coil cooling capacity also increases.Usually, the choice of the right against the face wind speed range between 2 ~ 3 m/s.From past experience, 2.5 m/s is a all aspects are suitable on wind speed, so the general as a selection criteria.If by higher coil head on wind speed to determine the windward area, can be relatively smaller coil shape and more compact units, system cost is lower.But when the wind speed is greater than 2.5 m/s, in the air conditioning unit must be equipped with water, in order to prevent the air will cold coil under wet conditions of the condensate into the system and the air duct.In addition, high wind speed can increase the resistance of the entire air system including coil, so you need to increase the total pressure of the air blower, makes the system power consumption and operation cost are increased.

2. Rows

Chilled water coil is commonly 4, 6 and 8 rows, row number, the more cold, the greater the amount of latent heat of the dehumidification capacity.In the selection, as long as can satisfy the requirement of processing the amount of cold air, should try to reduce the number of rows.Coil itself cost reduction not only so, and the air resistance is decreased, but also reduce the power consumption of the fan.

3. The piece from

Chilled water coil slice is apart from the general to 8, 10, 12, 14 pieces per inch.Piece number, the more cold, the greater the amount of air resistance.As a result, and the row number, as long as can satisfy the requirement of processing the amount of cold air, should try to reduce the number of finned coil

4. Loop 

Chilled water coil circuit half a HF, the whole circuit FL, dual-circuits power DB.Can be seen from the curve of the cooling capacity, under the same working condition, a half loop maximum cooling capacity, center of cold energy of the whole circuit, double the minimum amount of cold.But, due to the circuit is different, different water velocity of flow pipe, the different loop water pressure drop difference is very big.Maximum amount corresponding to the half loop water pressure drop and cold, the whole circuit pressure drop times, dual-circuits power minimum pressure drop.If the pressure drop is too large, can make the waterway system resistance increase greatly, thus the need to increase the pump power, increase the system operation cost.Serious water system will make it difficult to balance to meet the requirements of coil temperature in and out of the water.So in general, should control the coil pipe pressure drop within the 75 KP, pipe water flow rate to about 1 ~ 2 m/s suitable.Specific applications, small windward acreage of coil can choose half loop, so cold quantity can be bigger;Large windward area of coil choose whole circuit;Again big coil to select double circuit advisable to reduce the resistance of the water side.


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