Description
This paper presents data on the thermal performance of new LGWP developmental refrigerants (DRs) and of DRs/lubricant mixtures that are intended to be potential replacement candidates for R-410A. Heat transfer measurements were conducted for a horizontal copper tube commonly used in direct expansion evaporators of air conditioning systems with a 9.5 mm (0.375 in.) outside diameter and internally enhanced microfin surface. Data for the local two phase flow boiling heat transfer coefficient and pressure drop are presented for refrigerants R-410A, R-32, R-1234yf and two new DRs- referred to as DR-5 [R32/1234yf (72.5/27.5)] and DR-5A [R32/1234yf (68.9/31.1)]. Synthetic polyolester (POE) oil was added to the refrigerant mixtures to investigate the lubricant effects on heat transfer and pressure drop when the POE is used with the new LGWP DRs. The experimental findings indicated that the refrigerant R-32 had similar and slightly higher heat transfer coefficient than that of R-410A at the same refrigerant mass flux and heat flux conditions. Refrigerant R-1234yf had about 40 to 60% lower heat transfer coefficient than R410-A at a 4°C (39.2°F) saturation temperature. For this saturation temperature the developmental refrigerants DR-5 and DR-5A had heat transfer coefficients between R-32 and R-1234yf when the vapor quality ranged from 0.3 to 0.7. DR-5 and DR-5A showed identical characteristics in terms of pressure drop at both saturation temperatures of 4°C and 9°C (39.2°F to 48.2°F) to that of R-410A. The POE decreased the heat transfer coefficient of R-410A by 5 to 10% and it increased the pressure drop. Similar trends were observed for the other refrigerants but the lubricant penalization effects had different magnitudes. If the oil mass fraction in the refrigerant DR-5A/POE oil mixture was 3% by weight, then the presence of lubricant decreased the two phase flow boiling heat transfer coefficient by up to 5% and slightly increased the pressure drop.
Citation: ASHRAE Papers: 2015 ASHRAE Annual Conference, Atlanta, GA
Product Details
- Published:
- 2015
- Number of Pages:
- 8
- Units of Measure:
- Dual
- File Size:
- 1 file , 2 MB
- Product Code(s):
- D-AT-15-C027
