Load Calculations

[Raghurajsawhney]

That won't tell you the total capacity. Only the sensible. So its not nearly accurate on a fresh air system.

IF GPM of chilled water is same , what would be change in energy cost with reduced CFM across cooling coil?

[beenthere]

IF GPM of chilled water is same , what would be change in energy cost with reduced CFM across cooling coil?

How much did the chilled water delta through the coil change.

[Raghurajsawhney]

How much did the chilled water delta through the coil change.

Delta T is 6C

[beenthere]

If the chilled water delta remains the same at both CFMs, then there is no energy savings.

[Raghurajsawhney]

If the chilled water delta remains the same at both CFMs, then there is no energy savings.

In an Chilled water Air Handling unit

Situation 1

Supply air temp to coil = 35C
CFM = 5000
Supply air to Space 23 C at 5000 CFM

Chilled water Supply 4C
GPM 20

Chilled water return 8 C

Situation 2

Supply air temp to coil = 35C
CFM = 3000
Supply air to Space 23 C at 3000 CFM

Chilled water Supply 4C
GPM 20

Chilled water return NA

Question : 1. with decrease in CFM will there be change in Delta T of chilled water? And by how much approx.
2. What could be energy consumed in KWH in Situation 1 and Situation 2

Kindly share your thoughts. I am working on an energy saving project and would appreciate if you can help.

Thanks

[beenthere]

Unless I punched a number in wrong. Your first example shows a sensible air temp of 118,000 BTUs. But your chilled water only shows a 70,000 BTU change.

Need realistic numbers.

[heatingman]

In an Chilled water Air Handling unit

Situation 1

Supply air temp to coil = 35C
CFM = 5000
Supply air to Space 23 C at 5000 CFM

Chilled water Supply 4C
GPM 20

Chilled water return 8 C

Situation 2

Supply air temp to coil = 35C
CFM = 3000
Supply air to Space 23 C at 3000 CFM

Chilled water Supply 4C
GPM 20

Chilled water return NA

Question : 1. with decrease in CFM will there be change in Delta T of chilled water? And by how much approx.
2. What could be energy consumed in KWH in Situation 1 and Situation 2

Kindly share your thoughts. I am working on an energy saving project and would appreciate if you can help.

Thanks

There will be virtually no energy savings. Might be some, but very minimal. And as was pointed out, you need real life numbers, or a good computer model to know.

As you slow the fan, you will remove more moisture from the air. Unless the water temp is above the dew point of the air. And also you will increase the delta on the air side.

Delta on the water side would barely change.

The fan slowing pending on how its done can save electricity that way.

But on the chilled water side, you’d save more buy reducing flow on that end. This is the more typical approach. Control the water volume to meet desired space or air conditions. Fan speed typically manipulated for either dehumidification enhancement, building pressure requirements, or duct pressure requirements.


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[Raghurajsawhney]

Unless I punched a number in wrong. Your first example shows a sensible air temp of 118,000 BTUs. But your chilled water only shows a 70,000 BTU change.

Need realistic numbers.

I have just provided figures to depict a situation . Not any realistic figures. The delta T can be higher . you can do your calculations with change in chilled water BTU proportional to delta T change in Air

what is the formula/s to do such calculations.