It's vital to optimise the refrigerant charge for refrigeration and air-conditioning units. The attached are charging curves of a typical air cooler R290 unit with 5mm OD tube air coils based on modelling with RefrigLab cloud eTools (www.refriglab.com):
Fig(a): Both COP and cooling capacity are maximised with R290 charge of 140-148g. Refrigerant R290 entering into TEV is subcooled (SC>0, quality Xinlet=0, no bubbling) with charge >=130g.
Fig(b): Condensing and evaporating temperatures increase with the charging while suction vapour superheat decreases first during the undercharged period and increases slowly during the later overcharged process.
Fig(c): Compressor stores nearly half (42%-53%) of total R290 charge during the undercharged but condenser coil holds the largest during the last overcharged stage.
Any suggestions or comments on the modelling?
This post for discussion is a follow-up to my previous ones at LinkedIn:
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https://lnkd.in/gPbb8E7
https://lnkd.in/eBNvrYF
The following article may be useful to you.
Article An Experimental Investigation Into Alternative Refrigerants ...
Many research were optimized the refrigerant charge for the R&AC system's using maximum COP method. some alternate methods are minimum pull-down time test (minimum energy consumption) and exergy efficiency based charge optimisation. The following articles may be useful to you.
- F. Poggia,*, H. Macchi-Tejedaa, D. Leducqa, A. Bontemps, "Review Refrigerant charge in refrigerating systems and strategies of charge reduction:, INTERNATIONAL JOURNAL OF REFRIGERATION, 3 1 ( 2 0 0 8 ) 3 5 3 – 3 7 0.
- C. Aprea • A. Greco • A. Maiorino, "An experimental study on charge optimization of a trans-critical CO2 cycle".Int. J. Environ. Sci. Technol. (2015) 12:1097–1106. DOI 10.1007/s13762-014-0502-6
- J.M. Choi, Y.C. Kim, "The effects of improper refrigerant charge on the performance of a heat pump with an electronic expansion valve and capillary tube", Energy 27 (2002) 391–404.
- Prabakaran Rajendran, D. Mohan Lal" A novel exergy based charge optimisation for a mobile air conditioning system: An experimental study ", journal of thermal analysis and calorimetry, (2018) DOI: 10.1007/s10973-018-6998-0.
- Belman-Flores JM, Rodríguez-Munoz AP, Perez-Reguera CG and Mota-Babiloni A 2017, ‘Experimental study of R1234yf as a drop-in replacement for R134a in a domestic refrigerator’, International Journal of Refrigeration, vol.81, pp.1–11.
Thank you, Prabakaran! I will look at some of them that I did not before.
There are different coolers/freezers. Some products just operate at relatively stable ambient and product conditions and no pull-down operations are needed,, some require quick chilling/freezing, and some require minor pull-down capacity. Therefore, it depends on what your product designs require.
RefrigLab cloud eTools (www.refriglab.com) provide components designs and unit overall performance tuning including pull-down, ambient adaptation, charging optimising etc.
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