Abstract
Plate heat exchangers (PHEs) are used extensively in industrial applications and, owing to their compactness, and higher thermal efficiency, they are keys component of organic Rankine cycle (ORC) application. This study presents the experimental heat transfer characteristics during flow boiling of R245fa refrigerant with a commercial working fluid used in ORCs; inside brazed plate heat exchanger with chevron angle of 65 degree. The flow boiling heat transfer characteristics were measured with varying saturation temperatures, mass flux and heat flux, which range from 55.5 °C-61.8 °C, 15.5-17.4 kg m−2 s−1, and 6400-10120 W m−2, respectively. The experimental results showed that flow boiling heat transfer coefficient is dependent upon the heat flux and mass flux. The results showed that the heat transfer coefficient increases with the increase of heat flux, and then starts to decrease due to local dry out. However, at low mass flux, locally triggering dry out was more prominent than that high mass flux. The heat transfer coefficient showed to be sensitive to the change in the saturation temperature. Moreover, flow boiling heat transfer coefficient showed a linear relationship with mass flux of the refrigerant.
Highlights
Plate heat exchangers (PHEs) are used extensively for industrial applications, such as refrigeration, air conditioning, heating, cooling, etc
Among them, brazed plate heat exchangers (BPHEs) exhibits better sealing performance, higher resistant to corrosion and pressure and for these reasons are suitable for evaporation of refrigerants in small-scale organic Rankine cycle (ORC) plants [2], and this heat exchanger type is considered in this study
At low mass flux, i.e., G =15.5 kg m-2 s-1, this phenomenon is more prominent than that high mass flux
Summary
Plate heat exchangers (PHEs) are used extensively for industrial applications, such as refrigeration, air conditioning, heating, cooling, etc. PHEs consist of corrugated plates which provide a large effective heat transfer surface area as well as modification of the flow field in order to promote enhanced thermalhydraulic performance [1]. The research on the heat transfer performance in PHEs is fundamentally important in order to design heat exchangers for more efficient and economically viable ORC units [3]. D Han et al [4] performed experimental heat transfer studies in a BPHE using refrigerants R410A and R22 with varying the evaporation temperature 5 oC, 10 oC and 15 oC. G A Longo [5] investigated the effect of heat flux, mass flux, saturation temperature, outlet conditions on heat transfer and pressure drop during vaporisation of R1234yf refrigerant inside a BPHE.
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