Heat balance

[hinesguy]

In my previous thread I asked about heat balance and efficiency testing. Since i will have to talk about this next week with the auditor, I have a basic question. What would cause such an imbalance in evaporator tonnage to condenser tonnage. The tubes have been cleaned recently. The machine was designed to run with one pump. When we ran 2 pumps, it cured the imbalance. Any ideas?

 

[willard3]

Do you have any temperature and pressure drop data?

Imbalance is a very general question and, given the second law of thermo, condenser is going to reject more heat than the evaporator takes in.

 

[hinesguy]

The Dp for the condenser is around 3.4 but goes to 9 psi when 2 pumps are used. Temps are around 6 to 9 delta T.

 

[imok2]

You say the tubes have ben cleaned recently the question is were they brushed or were they acid cleaned or did you use tube scrapers as described below.

Tube Scrapers. A medium-pressure (300 psi)
water gun was used to propel Conco springloaded
metal scrapers through each condenser
tube. This technique was used in several tubes
prior to removal from the condenser. The scrapers
cleaned down to bare metal and polished the tube
surface for minimum flow restrictions. The plant
conducted one additional test to determine the
amount of aluminum-brass tube metal removed.
The water, deposits and scraper were collected
after a pass through, then filtered and analyzed.
The results indicated the integrity of the 18 gauge aluminum-brass tubing would not be
compromised.
: SOLUTION
The tube scraper method was selected as the approach that would provide the greatest
deposit removal with the least restriction to fluid flow. The unit was cleaned with Conco
tube scrapers at its annual overhaul. Conco C3S Tube Cleaners
Tube Wall Hard Deposits Soft Deposits
Tube Cleaner in Action. for more info go to:

http://www.google.com/search?hl=en&ie=ISO-8859-1&q=acid+cleaned+condenser+tubes

 

[hinesguy]

they where brushed with a Goodway. You think that they aren't clean enough and this is causing heat transfer probs. This is what I was thinking.