Cooling Water Heat
Cooling Water Heat
(OP)
In a 40 minutes batch process water in a closed loop is heated from 45 degC to 65 degC for first 10 minutes and then cools down to again 45 degC. The rate of temperature rise is attached. The flow rate is 200 m3/h. The heated water is cooled by a secondary circuit consisting of heat exchangers, cooling tower. pump etc as shown in the attached scheme.
To save huge amount of cost, my intention is replace the secondary circuit by providing a chilled water tank which will cool down the water to 45 degC. Chilled water is available in the plant at a temperature of 8-10 degC and a DeltaT of 5 deg is permissible. I want to find out what will be the total heat generation and the size of the chilled water tank.
I Think we are overdesigning the plant by taking the heat generation considering enthalpy at 65 degC and 45 degC which is practically not the case.
Any suggestion or help will be appreciated.
Regards
To save huge amount of cost, my intention is replace the secondary circuit by providing a chilled water tank which will cool down the water to 45 degC. Chilled water is available in the plant at a temperature of 8-10 degC and a DeltaT of 5 deg is permissible. I want to find out what will be the total heat generation and the size of the chilled water tank.
I Think we are overdesigning the plant by taking the heat generation considering enthalpy at 65 degC and 45 degC which is practically not the case.
Any suggestion or help will be appreciated.
Regards





RE: Cooling Water Heat
Regards
RE: Cooling Water Heat
Missing from any of this is any idea of the total mass of hot or cold water and size of the cold water supply.
At a simple level, you have a certain amount of heat energy you want to loose from the water (Mass X 20C x enthalpy of water) in about 25 minutes according to your graph. This gives you J/sec to be used to heat up your chilled water 5C and hence mass flow of chilled water required. Unless I'm missing something here (quite likely) this looks really quite straight forward so I'm not sure what the question is.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Cooling Water Heat
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. ùGalileo Galilei, Italian Physicist
RE: Cooling Water Heat
BUT. That chilled water costs a lot of money for each liter/gallon per minute because of the costs of pumping and the costs of the chill water refrigerator system and the hourly costs of the chill water refrigerator motor and refrigerant reloads and the chill water overhead heat losses in the lines and tanks. Are ytou really, really sure your economic analysis includes all of the costs of adding to the current chill water heat load?
RE: Cooling Water Heat
Now if I simply calculate Q=msDeltaT to find the size of the heat exchanger and the secondary water circuit including cooling tower, pumps, piping instruments etc. the cost of installation and maintenance is huge. I have a chilled water plant in my plant and have spare capacity which I wanted to utilize.
I believe I could be able to bring clarity on the problem.
RE: Cooling Water Heat
RE: Cooling Water Heat