Environmental Data Selection

[rize1159]

While designing a new plant, what should be selected values of dry bulb and wet bulb temperature while selecting an evaporative condenser for industrial application operating 24/7. ASHRAE has given its environmental data in Fundamentals as well as below link.
http://ashrae-meteo.info/index.php?lat=31.52&lng=74.40&place=%27%27&wmo=416410

Generally what environmental conditions are chosen for such application, 0.4%,1%,5%? Are they chosen from design column or monthly column.

[rize1159]

Can anyone share thoughts on this particular matter

[cricri]

Hi Rize 1159,
the usual value chosen by Baltimore, if no request from customer, is the higher WB value in 2% monthly time.

[Segei]

At 0.4% the difference is not significant 29.3C and 30.3C. What is going to be your condensing temperature (pressure)? This is the most important issue.

[RANGER1]

The piping is just as important as the correct selection of the equipment in multiple condensers.
This is a good document.



https://www.evapco.com/sites/evapco.com/files/2018-02/EvapcoPiping%20EvapCond131A.pdf (https://www.evapco.com/sites/evapco.com/files/2018-02/EvapcoPiping%20EvapCond131A.pdf)

[rize1159]

At 0.4% the difference is not significant 29.3C and 30.3C. What is going to be your condensing temperature (pressure)? This is the most important issue.

Without considering your wetbulb, how can we decide condensing temperature and pressure?

[Segei]

Look at this bulletin from Evapco https://www.evapco.com/sites/evapco.com/files/2017-05/191.phc_bulletin_0.pdf
Assume that design wet bulb temperature is 86F(30C). Heat rejection factor can be chosen as 2.47 and condensing temperature will be 95F(35C). If you choose heat rejection factor 2.25, condensing temperature will be 96.3F. Heat rejection factor is the most important part to achieve required condensing pressure. In this case I would choose 2.47. This is better for energy efficiency and it will better keep condensing pressure when heat transfer surface deteriorate.

[sterl]

You answered the fundamental question yourself: A food processing plant operating 24/7 cannot be subject to refrigeration shortages 5% of real time: And you don't know by what extent its going to be short without looking at the 1% and .4% values. If the 5% and 1% are wide spread, say 4-deg C. there is going to be a considerable proportion of real time when your industrial operation is going to be limping badly....On the other hand if this is a cold storage there are certain things that can be done when the weather gets that way to decrease load, but thats not practical with an active process...In most processes, the whole operation becomes a sinkhole for money when the throughput drops even marginally.

[NH3LVR]

I have been through this before.
I asked for a quote on a new condenser that operated a Spiral Freezer. On hot days the Screw Loading Percentage would back off due to head pressure (Motor Overload)
The Contractor insisted it was not worth the money when we only occasionally had an issue.
We also had a small Nitrogen Tunnel we used for overflow. A Vice President decided without consulting anyone that we should install a larger Tunnel. (Which worked well, until we got the bill for the Nitrogen!)