International Scientific Journal

Thermal Science - Online First

online first only

Analysis of heat transfer and irreversibility of ORC evaporator for selecting working fluid and operating conditions

Organic Rankine Cycle (ORC) is suitable. to converting the normally hard to utilize low-temperature thermal energies, such as geothermal energy, solar energy, and industrial waste heat, to electricity through utilizing low boiling organic working fluids. The performance of ORC system is dramatically affected by the selections of working fluid and working conditions. As a key component of waste heat recovery, the irreversible loss of evaporator also has great influence on the performance of ORC system. In this paper, we study the heat transfer performance in evaporator under the condition that the heat source parameters and pinch point temperature are identified. It is found that the heat transfer performance is affected by Cr, the ratio of heat capacity flow rates between the working fluids and the heat source fluid. We use the equivalent thermal resistance, deducing from the concept of entransy, to measure the irreversibility during the heat transfer process. Then, we define a parameter κr, the ratio between latent heat and sensible heat of working fluid, With the parameters Cr and κr, we investigate the relationship between the heat transfer and irreversible loss, and deduce the condition that maximum heat transfer and minimum equivalent thermal resistance occurs. Finally, a calculation method is established to choose the optimum working fluid and the evaporation condition.
PAPER REVISED: 2018-10-20
PAPER ACCEPTED: 2018-10-22
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