-
chiller efficiency
which design would be more helpful for energy saving in chiller operation?
a chiller with screw compressor using sliding valve to modulate the flow rate according to real load, (unloading the compressor)?
or
a chiller with VFD installed on lead compressor?
i have seen both in operation and believe me, unnoticeable difference between both.
my decision would be on price and complexity of system. i would go modulating valve.
what you think?
-
-
Why not a screw with vfd?. What is your load profile & number of chillers?
Mfg or sales rep would have to run an analysis.
-
i am a mfg
screw with vfd, i have done it once. the cost of chiller like 15% more. for no big reason.
the sliding valve will save energy if compressor start unloading and work in partial capacity. the same for vfd, the chiller will save energy during low load by lowering the compressor induction motor speed.
if working between 80%-100% of compressor capacity, then the sliding valve would be slightly more efficient,.. if working bellow 80% capacity, then the vfd would be more efficient solution. but the difference between power consumption in both option is not that big (unless compressor working most of the time at 50% capacity or bellow then VFD can be a good solution with very long ROI)
but service and maintenance and cost of repair parts will be huge in case of VFD
-
Post Likes - 1 Likes, 0 Dislikes
-
"but service and maintenance and cost of repair parts will be huge in case of VFD" In the case of slide valve modulations over "almost excessive" varying loads the potential for repairs tend to increase with slide valve components, solenoids and controls. If the anticipated load is projected to be constant, such as a process cooling application, then slide valves would tend to sit fairly stable. However, stable positioned slide valves tend to wear at shafts and sleaves due to continued harmonics. In the case of a VFD drive with slide valve unit the slide valve opens to 100% after system stabilization, then the VFD ramps to required speed. In the case of no slide valve and only VFD control system, stability requires specific control parameters to create and maintain compression ratios. Things like chill water and condensor water flow rates, tower water temps, temperature resets and drastic load variations (such as process cooling application) tend to need a bit more attention with a true VFD screw machine. Having said all that, the statement about maintenance basically comes down to mechanical or electrical costs. In terms of not considering efficiency history, I always felt that a seven-year plan would include a drive replacement. Considering all of the possible field encountered scenarios, my experience from a service point of view, favored a slide valve and VFD combination.
-
Originally Posted by
mohad_i
which design would be more helpful for energy saving in chiller operation?
a chiller with screw compressor using ...
what you think?
Are Cooling Towers used in Saudi Arabia ?
IF Yes, then USE a Water-Cooled Chiller.
Designer Dan __ It's Not Rocket Science, But
It is SCIENCE with
Some Art. _ _
KEEP
IT
SIMPLE &
SINCERE ___ __
www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities
-
Originally Posted by
dan sw fl
Are Cooling Towers used in Saudi Arabia ?
IF Yes, then USE a Water-Cooled Chiller.
Have to use desalination process for condenser water. Has to figure into operating cost.
-
To me, the second variant is better if we talking about energy effiency
-
To me, the second variant is better if we talk about energy efficiency
-
But it's costly to repair.
-
The most energy efficient chillers on the markets have to be anything running with the Danfoss oil free Turbocor ( centrifugal type ). These machines can run at low compression ratios, they use mechanical & VSD speed reduction to unload the compressor down to 30% and parts are readily available also.
-
Turbocor compressors have limited unloading and most sizes require hgbp for practical applications.
Review the compressor operating envelopes for each model, varies a good bit.
Their software limits low differential operations, keeping them in choke. Extended operation in choke mode can cause rotor failures due to demag.
-
YMC2 if you can advantage of low entering condenser water temps. They can get down to 15% turndown and lower if needed but not really recommended for extended running.
Find it comical the guy posting from Saudi and worried about costs. They've just laid out a boat load of cash for Neymar of all people.
-
The NPLV rating serves as a valuable indicator for determining the most energy-efficient chiller. This is due to its inclusion of both design efficiency and part load efficiency.
-
During a recent participation in the chiller selection process for an air-cooled chiller, I conducted a comparison between non-VFD and VFD screw chillers from Trane (RTAG), Carrier, and Daikin. Notably, the NPLV difference between the non-VFD chiller with a slide valve and the VFD chiller with a slide valve from Trane were 0.76 KW/TON and 0.59 KW/TON, respectively. This observation underscores the substantial impact that VFD has on chiller performance.
Reply
Professional Member*
ksefan liked this post.
