Questions about Chiller Design

[Vincent Yu]

Hello everyone,

Currently I am working on designing a chiller system to provide 30 degree Fahrenheit glycol. Evaporating temperature is about 20 Fahrenheit. The total cooling capacity is 80 tons. I plan to use 9 ten-ton refrigeration systems. One unit is a backup. I would like to use scroll compressors in my design. My questions are:

1. At 20 degree Fahrenheit evaporating temperature, which refrigerant is better, R404 or R507? Which refrigerant is more efficient and easier to maintain?

2. I have two options for the condenser: one option is using remote air cooled condenser. The other one is using water cooled condenser and all the 9 chillers share a cooling tower. I wonder which one is the right way to go.

Please advise if you have any ideas about these questions.

Many thanks

[The Viking]

I will steer clear of the refrigerant issue, no doubt others will pick it up shortly.

Condenser?
You have selected 9 individual units with one in standby at all times should one fail. What will happen if the cooling tower or it's associated water works goes down?

[botrous]

1. At 20 degree Fahrenheit evaporating temperature, which refrigerant is better, R404 or R507? Which refrigerant is more efficient and easier to maintain?

Hi . . .

First what is your condensing design tempreture???
Knowing the condensing design temp. is critical, once you choose it go for the pressure enthalpy chart and choose the refrigerant with minimum pressure difference between evaporating and condensing tempretures.

see delta H and go for the greater . . .
You should do a certain exchange between delta H and minimum evaporating condesnsing pressure . . . do it carefully.

The greater delta H of evaporator =>less flow.
The smaller delta p ==> smaller compression ratio.

Respects and regards

[botrous]

I will steer clear of the refrigerant issue, no doubt others will pick it up shortly.

Condenser?
You have selected 9 individual units with one in standby at all times should one fail. What will happen if the cooling tower or it's associated water works goes down?

Totaly agree

[Vincent Yu]

I will steer clear of the refrigerant issue, no doubt others will pick it up shortly.

Condenser?
You have selected 9 individual units with one in standby at all times should one fail. What will happen if the cooling tower or it's associated water works goes down?

This is a good point. Thanks

[Lc_shi]

Maybe you can consider to apply evaporative condenser.

[wambat]

AS far as which refrigerant to use for most systems, Honeywell recommends Genetron 404A® or Genetron® AZ-50® (R-507) refrigerants. These products are similar in composition and performance. The key difference is that R-507 is an azeotrope that can be used in flooded evaporators, and has no glide and can be easily recycled or reclaimed without a resulting change in composition.

[Chillin']

If you have a choice, always go with water cooled. Just make sure that the cooling towers are always on when you need the chiller, and also ensure your towers have enough capacity.

Cheers!

[winfred.dela]

1. At 20 degree Fahrenheit evaporating temperature, which refrigerant is better, R404 or R507? Which refrigerant is more efficient and easier to maintain?

2. I have two options for the condenser: one option is using remote air cooled condenser. The other one is using water cooled condenser and all the 9 chillers share a cooling tower. I wonder which one is the right way to go.

Please advise if you have any ideas about these questions.

Many thanks

Item 1. R404 or R507
- I usually use R507 because the glide is 0.

Item 2. air cooled or water cooled.

- I usually use air cooled because the 10 TR condensing unit (ACCU) is readily available in the market. Each compressor with 1 condenser and fan.
- For lower cost chiller, you may consider buying an aircon ACCU. Just check compressor model if suitable.

[abet_meneses]

vincent,
just go for the air cooled condenser.water cooled condenser has high overhead operting expenses compare with air cooled.