Analysis of heat transfer and irreversibility of organic rankine cycle evaporator for selecting working fluid and operating conditions

Abstract

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 difference are identified. It is found that the heat transfer performance is affected by C r , the ratio of heat capacity flow rates between the working fluid and the heat source fluid. The equivalent thermal resistance, deducing from the concept of entransy, to measure the irreversability during the heat transfer process is used. Then, the parameter κ r , the ratio between latent heat and sensible heat of working fluid is defined. With the parameters C r and κ r , 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.

Modification of Kalina cycle system 34g by replacing throttle valve with single-screw expander

“…Among all technologies, the Organic Rankine Cycle (ORC) and the Kalina cycle (KC) are two popular ones and extensive research has been conducted on the ORC and KC for the past few decades [1][2][3][4]. The research hotspot of the ORC mainly includes two aspects: working fluid selection and parameters optimization [5][6][7]. However, the thermodynamic performance of an ORC with a pure working fluid is low due to its evaporation and condensation at constant temperature.…”

Comments on “Analysis of heat transfer and irreversibility of ORC evaporator for selecting working fluid and operating conditions”

“…Ye et al [1] studied the performance of heat transfer in evaporator under the case that the parameters of heat source and temperature of pinch point were identified. In their 1 st figure, Ye et al [1] utilized the graphical method of T-Q diagram analysis for preheating pinch point and vaporizing pinch point. In their 24 th equation, Ye et al [1] introduced the definition of entransy principle to use it in their analysis.…”

“…In their 1 st figure, Ye et al [1] utilized the graphical method of T-Q diagram analysis for preheating pinch point and vaporizing pinch point. In their 24 th equation, Ye et al [1] introduced the definition of entransy principle to use it in their analysis.…”

“…Firstly, Ye et al [1] concealed the origin of the graphical method of T-Q diagram analysis. The T-Q diagram analysis belongs to Professor Adrian Bejan, who first proposed it in 1977 as graphic techniques for teaching engineering thermodynamics [2].…”