How does a SLHX impact refrigerant charge?
The attached diagram shows the results from a typical air cooler's R290 unit: The unit R290 total charge decreases with the increase of SLHX vapour superheat. When the superheat is greater than 20K, the unit R290 total charge is less than 150 grams. With the increase in SLHX's heat transfer area (e.g., flow channel length), superheat of suction port refrigerant vapour increases so the refrigerant mass dissolved to compressor lubricant oil decreases while the refrigerant quantities stored in condenser and evaporator 5mm OD coils have relatively small changes as displayed in the diagram.
This is part of my LinkedIn Posts about SLHX (Suction Line Heat Exchanger) with the link https://lnkd.in/gPbb8E7 and https://www.linkedin.com/feed/update/urn:li:activity:6445911044706697216 and about refrigerant charge minimisation with the link https://lnkd.in/g68uaJW based on the cloud eTool calculations ( www.refriglab.com ). Please click these links for further details. Your critical comments will be much appreciated.
Is a SLHX really required in a low charge RAC unit?
I suggest you checking this paper. It may help you.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1004.9991&rep=rep1&type=pdf
Hi,
I can download it. The paper is for Ren, Tao; Wu, Guoming; Ding, Guoliang; Zheng, Yongxin; Gao, Yifeng; and Ji, Song, "Investigation of Application of Suction Line Heat Exchanger in R290 Air Conditioner with Small Diameter Copper Tube" (2014). International Refrigeration and Air Conditioning Conference. Paper 1407.
http://docs.lib.purdue.edu/iracc/1407
What about the compressor work consumption?. Did you calculate it?
The calculation of the compressor's compression work is included in the cloud eTool [CompS] available at www.refriglab.com. Please access the link for further details and take trials free of charge.
In addition, with the increase of suction superheat, the refrigerant mass dissolved to the compressor lubricant oil decreases so does the unit refrigerant total charge. This is what the post is focused on.
How do you know that the amount of refrigerant dissolved in the lubricant oil decreased?
The solubility of refrigerant like R290 in POE32 for example can be calculated using the compressor suction temperature and pressure, i.e., the function equation y=f(x1,x2). The solubility equations are available from lubricant companies or compressor companies. Hopefully this helps.
Dear Jeff,
Do you have any experience with using both SLHX and cap tube suction line heat exchange together? What is impact of this combination on COP of the system? Any research paper / patents / documents will be appreciated.
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