Water Flow in evaporator exceeds the factory rating, what will happen?

[aryramadhan]

I wanna know what will happen if the water flow in the evaporator is exceed the factory rating? will the heat transfer from the water to the refrigerant less effective? or other wise?

because from the data in my case study for my final project in my university, said so.. the rating from the factory is 114 m3/hr.. but the actual measured data is around 185 m3/hr..

sorry for my bad English , any help appreciated. thx before

[frank]

Lets look at the numbers:

114 m3/hr = 114000 l/hr = 31.666l/s

So, assuming that this is a water chiller with a 6K dt across the evaporator we would get:

Q = 31.666x4.19x6

therefore Q = 796kW

So, for a chiller rated at 796kW with an increased flow rate of 185m3/hr (51.388l/s) we would get :

dt = 796/(51.388*4.19)
=3.9
So, an increased flow rate across the evaporator results in a decrease in refrigeration effect






:

[Andy]

Lets look at the numbers:

114 m3/hr = 114000 l/hr = 31.666l/s

So, assuming that this is a water chiller with a 6K dt across the evaporator we would get:

Q = 31.666x4.19x6

therefore Q = 796kW

So, for a chiller rated at 796kW with an increased flow rate of 185m3/hr (51.388l/s) we would get :

dt = 796/(51.388*4.19)
=3.9


So, an increased flow rate across the evaporator results in a decrease in refrigeration effect






:
Hello Frank:)

are you sure? Will the leaving temperature not just become closer to the entry temp.

Kind Regards Andy :)
Q = M *C*DT

796/(51.388*4.19)= 3.6969

[NoNickName]

There is no detrimental effect on performance whatsoever, but a quicker erosion of the tube bundle that will soon lead to failure of tubes and chiller write off.

[frank]

Hello Frank:)

are you sure? Will the leaving temperature not just become closer to the entry temp.

Kind Regards Andy :)
Q = M *C*DT

796/(51.388*4.19)= 3.6969
Exactly Andy. The dt will become smaller for the entering and leaving temps

[Magoo]

Hi
Generally the manufacturer does not supply info on flow rates, just anoy you. The are for the optimum for performance, added is an acceptable fouling factor.
So if the flow is exceeded, it won't perform to design.
Tube velocities and thermal transfer rates are out the window.
Suggest you regulate the outfeed water valves to the recommended water pressure differential. And get chiller working correctly. Otherwise you are wasting energy, and not getting the required supply water temps for duty designed.
If high circulation volumes requiredconsider a parrallel by-pass that covers both problems.
magoo

[desA]

^ A very sensible post.

Exactly, regulate the water flow to the rated velocity (preferred), or install a bypass to manage the excess flow.

[aryramadhan]

wow thx guys for the replies..
yeah the measured DT is way below the rating.. the rating are for inlet temp 12 deg C and 7 deg C for the outlet.. but the measured temp for inlet is around 15 deg C and the outlet is around 13..

alright maybe all try to control the flow. but what worries me that will head of the pump meet its requirement. because the chiller and the pump is on the basement floor and it's an eight storey building..

ok i try to calculate the pump first. there some other things that i like to ask because i found some abnormalities in my data. but i'll keep it for later i'll try to figure it out my self first..

thx guys