Abstract
A database for flowing condensation of three hydrocarbons, namely propane (R290), isobutane (R600a), and propylene (R1270), is extended by experimental tests in a smooth tube and two microfinned tubes with an increase of heat exchange area of 1.51 and 2.63, respectively. The outer diameter for all of the test tubes was 5 mm. Heat transfer coefficient and pressure drop are compared between the fluids and tubes. Tests were conducted at saturation temperatures of 35 °C and mass fluxes between 200 to 500 kgm−2s−1. Results show that isobutane (R600a) has a higher heat transfer coefficient and pressure drop while propylene (R1270) and propane (R290) present very similar characteristics. Both microfinned tubes increase the heat transfer coefficient compared to the smooth tube, but with different magnitude and tendencies and almost independently of the fluid tested. The maximum increase of heat transfer coefficient reached values of up to 1.8 while the maximum increase in pressure drop was by a factor of 1.7. Data have been compared with predictive methods exhibiting accurate correlation for smooth tube, while the accuracy of results for the microfinned are dependent on the type of tube and fluid used.
Highlights
The refrigeration industry has been challenged by its effect on the environment
The results show that R290 and R1270 have similar behavior in the tested mass fluxes while the HTC of R600a is considerably higher
There is always an increase in the HTC for microfinned tubes compared to the smooth tube
Summary
The refrigeration industry has been challenged by its effect on the environment. This problem is exacerbated by the current generation of working fluids that have an exceptionally high Global Warming Potential (GWP). The progress toward a more sustainable and environmentally friendly refrigeration industry requires a broad shift in the utilized working fluids to have a low GWP and zero Ozone Depletion Potential (ODP). Propane (R290), isobutane (R600a), and propylene (R1270) have long been used as working fluids in various applications. Hydrocarbons offer favorable saturation curves befitting different use cases while enjoying low GWP and zero ODP. The use of hydrocarbons in refrigeration systems has been long limited by flammability concerns
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