Browsing by Author "Kuo, Chi-Ron"

Now showing 1 - 4 of 4

Analysis of a 50 kW organic Rankine cycle system
(2011-10-01)
Kuo, Chi-Ron
;
Hsu, Sung-Wei
;
Chang, Kai-Han
;
Wang, Chi-Chuan
;
機械工程學系
This study analyzes the system performance of a 50 kW ORC system subject to influence of various working fluids. A dimensionless "figure of merit" combining the Jakob number, condensing temperature, and evaporation temperature is proposed for quantitatively screening working fluid as far as thermal efficiency is concerned. The thermal efficiency normally decreases with the rise of figure of merit, and the predictive ability of the proposed figure of merit is not only applicable to the present eighteen working fluids but is also in line with some existing literatures. Analysis of the typical ORC heat exchangers indicates that the dominant thermal resistance in the shell-and-tube condenser is on the shell side. Similarly, the dominant resistance is also on the refrigerant side for the plate evaporator. However, there is a huge difference of thermal resistance amid working fluid and water side in the preheating zone. Conversely, only a minor difference exists in the evaporation region. The extremely uneven resistance distribution in the plate heat exchanger can be resolved via an additional preheater having significant augmentation in the working fluid. (C) 2011 Elsevier Ltd. All rights reserved.
Dynamic Response of a 50 kW Organic Rankine Cycle System in Association with Evaporators
(2014-04-01)
Lee, Yuh-Ren
;
Kuo, Chi-Ron
;
Liu, Chih-Hsi
;
Fu, Ben-Ran
;
Hsieh, Jui-Ching
The influences of various evaporators on the system responses of a 50 kW ORC system using R-245fa are investigated in this study. First the effect of the supplied hot water flowrate into the evaporator is examined and the exit superheat on the system performance between plate and shell-and-tube evaporator is also reported. Test results show that the effect of hot water flowrate on the evaporator imposes a negligible effect on the transient response of the ORC system. These results prevail even for a 3.5-fold increase of the hot water flowrate and the system shows barely any change subject to this drastic hot water flowrate change. The effect of exit superheat on the ORC system depends on the type of the evaporator. For the plate evaporator, an exit superheat less than 10 degrees C may cause ORC system instability due to considerable liquid entrainment. To maintain a stable operation, the corresponding Jakob number of the plate heat evaporator must be above 0.07. On the other hand, by employing a shell and tube heat evaporator connected to the ORC system, no unstable oscillation of the ORC system is observed for exit superheats ranging from 0 to 17 degrees C.
Response of a 50 kW Organic Rankine Cycle System Subject to Influence of Evaporators
(2014-01-01)
Lee, Yuh-Ren
;
Kuo, Chi-Ron
;
Liu, Chih-Hsi
;
Fu, Ben-Ran
;
Wang, Chi-Chuan
The variations of the evaporator on the system responses of a 50 kWe ORC system using R-245fa are investigated. The effect of exit superheat on the ORC system depends of the types of the evaporator. For the plate evaporator, an exit superheat less than 10 degrees C may cause ORC system unstable due to liquid entrainment. For maintaining stable operation, the corresponding Jakob number of the plate heat evaporator must be above 0.07. On the other hand, no unstable oscillation of the ORC system is observed for an exit superheat of 0 similar to 47 degrees C when the shell-and-tube heat exchanger is used as the evaporator. (C) 2014 The Authors. Published by Elsevier Ltd.
Transient response of a 50 kW organic Rankine cycle system
(2012-12-01)
Lee, Yuh-Ren
;
Kuo, Chi-Ron
;
Wang, Chi-Chuan
;
機械工程學系
;
Department of Mechanical Engineering
This study examines the transient responses of a 50 kW ORC (Organic Rankine Cycle) system subject to change of the water coolant in the condenser with R-245fa as the working fluid. With a moderate increase or decrease of water coolant flow rate, all the major quantities such as the output power, condensing pressure, evaporation pressure show mild transition. The mass flow rate of the R-245fa remains roughly the same during the transient. For a sharp rise of the water coolant flow rate, the ORC system undergoes a rather unusual behavior. The output power is first slightly increased, followed by a sharp decline to barely any output power and remains there until the end of the transient. The output power increased back right after the transient and exceeded its original state. There is almost no R-245fa mass flow rate during the power outage period. Yet the evaporation pressure also experienced a gigantic falloff during the transient period. This peculiar surge phenomenon is related to tremendous change of the total void when condensation takes place that momentarily reduces the R-245fa mass flow rate. The surge effect caused by the water coolant is associated with the rate of variation in the overall heat transfer coefficient. (C) 2012 Elsevier Ltd. All rights reserved.