Byung-sik Park

Keywords: Recuperated Organic Rankine Cycle Regenerative Organic Rankine Cycle Thermo-economic optimization a b s t r a c t Present study deals with the comparative assessment of three different configurations of ORC (Organic Rankine Cycle) system including basic ORC, recuperated ORC, and regenerative ORC system for low temperature geothermal heat source. The comparison of the performance of each cycle is carried out at their optimum operating condition using Non-dominated Sorting Genetic Algorithm-II for minimum specific investment cost and maximum exergy efficiency under logical bounds of evaporation temperature , pinch point temperature difference and superheat. Objective functions are conflicting, therefore, optimization results are presented in the form of a Pareto Front Solution. Thermal efficiency and the exergy efficiency for recuperated and regenerative are higher than basic ORC but with an additional average specific investment cost of 3% for basic and 7% for regenerative cycle. Working fluids with critical temperature in the same range of heat source results in better thermal performance. R245fa has highest Exergy efficiency of 51.3% corresponding to minimum specific cost of 2423$/kW for basic cycle, 53.74% corresponding to 2475$/kW for recuperated, and 55.93% corresponding to 2567$/kW for regenerative cycle.

A recuperative, burner in the capacity of 400kW was designed using the design data from the experimental results. Performance tests on this burner were made. The exhaust gas analysis, including NOx, the measurement of the flame temperature and velocity in the recuperative burner were the main topics of hot combustion tests. Design data from the experimental results are the gas velocity, air velocity, the tip location of gas nozzle and the dimension of furnace. In view of uniform temperature distribution and thermal efficiency, it is appropriate to maintain the furnace pressure at 2-3mmAq.

Low-grade waste heat recovery technologies reduce the environmental impact of fossil fuels and improve overall efficiency. This paper presents the economic assessment of greenhouse gas (GHG) reduction through waste heat recovery using organic Rankine cycle (ORC). The ORC engine is one of the mature low temperature heat engines. The low boiling temperature of organic working fluid enables ORC to recover low-temperature waste heat. The recovered waste heat is utilized to produce electricity and hot water. The GHG emissions for equivalent power and hot water from three fossil fuels—coal, natural gas, and diesel oil—are estimated using the fuel analysis approach and corresponding emission factors. The relative decrease in GHG emission is calculated using fossil fuels as the base case. The total cost of the ORC system is used to analyze the GHG reduction cost for each of the considered fossil fuels. A sensitivity analysis is also conducted to investigate the effect of the key parameter of the ORC system on the cost of GHG reduction. Throughout the 20-year life cycle of the ORC plant, the GHG reduction cost for R245fa is 0.02 $/kg to 0.04  $/kg and that for pentane is 0.04 $/kg to 0.05 $/kg. The working fluid, evaporation pressure, and pinch point temperature difference considerably affect the GHG emission.

Present study deals with the development of hydraulic and thermal design model of chevron type plate evaporator and optimization of its geometrical parameters for a low temperature geothermal ORC system. The optimization is performed using Non-dominated Sorting Genetic Algorithm-II (NSGA-II). The primary geometrical parameters of evaporator are selected as decision variables which include length, width and plate spacing. The minimum cost of evaporator and minimum pressure drop are chosen as objective functions under restriction of constant amount of heat transfer. Since the objective functions are conflicting, a single value of decision variables cannot satisfy both objective functions simultaneously. Therefore optimization results are presented in the form of Pareto Front solution which is trade-off between pressure drop and cost of evaporator. The minimum cost evaporator is 1570$ corresponding to pressure drop of 125 kPa while the maximum cost is 6988$ corresponding to a pressure drop of 5.2 kPa. The sensitivity analysis shows that the plate length has promising effect on pressure drop and cost of evaporator. Furthermore, the effect of pressure drop on cost of evaporator and net power of ORC system is also investigated. The optimum value of allowable pressure drop is 30e40 kPa, corresponding to net power of 73e74 kW of ORC system and cost of evaporator 3000e3500$.

ABSTRACT Waste heat recovery from the exhaust gas of industrial furnaces and kilns that are high energy-consuming equipment is one of the effective energy conservation methods because of its high sensible heat contents. The recuperative burner integrated with a recuperator and burner is one of the combustion equipments with many advantages of simple installation, compactness and easy control which can be applied to various fields of industry. A recuperative burner with the capacity of 400 kW was designed using the design data from experimental results. Performance tests on this burner were made. The exhaust gas analysis, including NOx, the measurement of the flame temperature, velocity, heat flux and heat flux analysis on the recuperative burner were the main topics of hot combustion tests. Design data from the experimental results are gas velocity, air velocity, air velocity, the tip-location of gas nozzle, the dimension of furnace suitable to burner capacity, the dimension of recuperator and the role of cross-shaped steel plate for increasing the energy efficiency in the recuperator. For uniform temperature distribution and good thermal efficiency, it is appropriate to maintain the furnace pressure at 2–3mmAq. © 1998 John Wiley & Sons, Ltd.

This work presents an experimental investigation of a small scale (1 kW range) organic Rankine cycle system
for net electrical power output ability, using low-grade waste heat from steam. The system was
designed for waste steam in the range of 1–3 bar. After the organic Rankine cycle system was designed
and thermodynamic simulation was performed, equipment selection and construction of test rig was
carried out. R245fa was used as working fluid, a scroll type expansion directly coupled with electrical
generator produced a maximum electrical power output of 1.016 kW with 0.838 kW of net electrical
power output. The thermal efficiency of the system was 5.64%, net efficiency was 4.66% and expander
isentropic efficiency was 58.3% at maximum power output operation point. Maximum thermal efficiency
was 5.75% and maximum expander isentropic efficiency obtained was 77.74% during the experiment.
Effect of superheating of working fluid at expander inlet was also investigated which show that an
increase in the degree of superheating by 1 C reduces thermal efficiency of system by 0.021% for current
system. The results indicated that the measured electric power output and enthalpy determined power
output (after accounting for isentropic efficiency) differed by 40%. Similarly, the screw pump converted
42.25% of electric power to the enthalpy determined pumping power delivered to the working fluid. Both
expander and screw pump were losing power in electric and mechanical losses (generator/motor) presenting
a need of further development of these components for better efficiency. Heat loss in piping is
also a factor for improving efficiency along with the ability of heat exchangers and control system to
maintain the least possible degree of superheat of working fluid at expander inlet.