4 replies to this topic

[ayan_dg]

For an air cooler (induced draft or forced draft) can any one tell me what percentage of natural cooling can be considered. In other words when the fan power goes off how much cooling can be considered.

[fallah]

For an air cooler (induced draft or forced draft) can any one tell me what percentage of natural cooling can be considered. In other words when the fan power goes off how much cooling can be considered.

Around 20 percent of Rated Capacity.

[ankur2061]

For an air cooler (induced draft or forced draft) can any one tell me what percentage of natural cooling can be considered. In other words when the fan power goes off how much cooling can be considered.

I don't think your question is very relevant. An air cooler is designed for a specific duty considering ambient air temperature for the location where the air cooler is located. I am very sure that if the fan stops due to power failure, you will not be able to maintain your temperature at the cooler outlet and hence the percentage cooling question doesn't make much sense. Power failure also means that the other equipment connected to the air cooler will also stop functioning and the situation leads to an emergency shutdown of the unit/plant due to power failure. For critical services, which may or may not include an air cooler, to avoid such a situation a UPS system is provided which ensures that all critical equipment requiring electric power do not face such a situation. Hence I don't see the point of your question in a real life industry situation.

For mechanical reasons, i.e. maintenance of the fan many operating companies specify two fans (1W + 1S) per bay of the air cooler, so that if one fan is under mechanical maintenance, the other fan can fulfill the duty requirements of the cooler.

If this is simply an academic exercise, then I think you probably need to talk to some air cooler vendors to get an answer.

Regards,
Ankur.

[ayan_dg]

Ankur,
The information is relevent when you want to give DT (design temprature) of upstream piping and downstream piping for an air cooler. Also in calculating relieving load and condition for relief downstream of the air cooler . for a bigger air cooler this is very relevent.

[fallah]

Please note to paragraph 5.6.4 Air-cooler fan failure of API 521.

I think ayan_dg is questioning to take credit for partial condensing capacity due to natural convection in the case of fan failure.Based on this he/she can determine relevant relief rate.