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arun.hvac
05-08-2009, 09:59 AM
hello friends,
I am doin my Mechanical engineering and new to this refrigeration field, I am doing a project on the optimization of the centralized air conditioning system in a jewellery industry.
My manager said me to work on it, so that I can increase its efficiency or reduce the refrigeration load by suggesting any modifications.
I am interested in calculating the total refrigeration load of the plant i.e TR( ton of refrigeration) required by the plant.
I would like you people to help me in this process.
It ll help me a lot, as I am alone in working.
please suggest me the important tasks which are need to be done in this project.

arun.hvac
05-08-2009, 11:03 AM
I am calculating the TR of each AHU unit in the plant, I m just taking the DBT and WBT of air at the inlet & outlet conditions of AHU, from these I m finding the difference in their enthalpies. Air flow is measured with help of anemometer. Finally I am finding the net heat transfer in the AHU's respectively.

arun.hvac
05-08-2009, 11:06 AM
While calculating the air flow, The denisty of air is being taken as the average of both inlet and outlet conditions..Is it correct??
I m planning to these procedure for all the 14 AHUs in the plant.
Then I ll compare the total AHUs TR and Chillers TR.
please some one tell me wat to do next??

Tesla
06-08-2009, 12:00 AM
Hi arun
Those AHUs should have a data plate with KW of model numbers to look up KW on OEM data sheets. If it is an older central plant system you would look at installing VSDs on the fans and pumps, and raising the chilled water setpoint. The ultimate conditions to achieve is load matching. Most systems are designed to operate on the highest load (or 95% of) but the load is more often half of this. You will be limmited by the mechanics of your system ie mininum air flows, fresh air, operating parameter limits of compressors etc. I have seen some expensive stuff ups in this area form so called engineers and consultants so be careful. You need to prove the savings not just make them. See if you can get a power profile of the central plant possibly from power supplier with clients permission. Check running times verses occupied times, warm up and cool down periods. You will need to look at each system component potential efficiency then look at the overall system which will be less, it's no good saving 50% power consumption of the chiller when the fans, pumps, cooling tower etc loose 50%. Another thing is the life cycle of system and comonents, capitol expenditure, and payback period/return on investment.

arun.hvac
06-08-2009, 05:03 AM
Hello sir,
Thank you very much for the valuable reply. :)
I ll start working with your valuable guidance.
I ll calculate the efficiency of each component.

Yes, I can get the power profile of the plant.

"Check running times verses occupied times, warm up and cool down periods."

Can you please explain it in detail, I didn't get it. :(

I am also interested in reducing the TR required by the plant by identifying any losses. Can you provide me some information regarding the data collection and calculations regarding this.

Tesla
07-08-2009, 01:29 AM
OK
From the power profile you will see when the plant starts (in the morning) and when the plant stops at night - this is the plant running time. The occupied time is the time when people are in the building (working). The warmup time is how long it takes for the plant to achieve desired temp conditions, and cooldown is when you could stop the plant before people leave the building. The plant has inertia and it takes time to cool/heat the building, ie you could stop the plant at 4pm when people leave the building at 4:30pm. This depends on the type (DX/CHW) and size of plant and type of control system installed.
As for your second question there are many possible answers. Is there simultanious heating and cooling? reduce it. Can you reduce the solar load through glass and roof with shades or reflectors? Controls are usually the cause of over heating/cooling with thermostats/sensors out of calibration, located in the wrong position, or someperson/s got the window open with a heater under bench, Too much/little air. ventilation?. you will find many ways to save power BUT not all save money - it might cost more for the modification. So focus on the bigest bang for your clients buck. You can download (at a small cost) from the Australian Standards website a paper on enrgy audits which is a helpfull guide. Keep the big picture in mind and think plant life cycle, ie you may reccomend the compressors be replaced with XXtype in five years time or when the plant should be upgraded.

arun.hvac
07-08-2009, 05:29 AM
Sir,
Thanx a lot for your valuable guidance and detailed explanation for my queries.
It is used only for cooling as the ambient temperature here is never below 22 C.
Regarding the reduction of solar load,they have already planted some trees on the roof,I m thinking of Cool roof implementation will also help in reducing the load.
I ll work on it and let you know the results of my work. :)