Vol. 18 No. 2 (2003)

Sub-channel analysis is a method for analyzing thermal hydraulic aspects of nuclear reactors or heat exchangers. The analysis calculates distributions of fluid temperature, pressure, axial velocity, transverse velocity, and fuel rod temperature or heat flux. This paper deals with efforts for improving the accuracy of the sub-channel method. Three numerical schemes for evaluating transversal advective heat rates, i.e.: up wind, exponential, and central difference schemes, were compared. The differences among calculation results obtained by programs that apply these schemes were insignificant.…

Hydrocarbon refrigerant is one kind of refrigerants, which is developed to substitute CFC and HCFC. The substances contained in hydrocarbon refrigerant are etane, propane, normal butane, and iso butane. Ethane is being suspected on reducing the performance of refrigerator. This paper deals with theoretical study of ethane influence in hydrocarbon refrigerant. First of all it is necessary to create software for evaluating thermodynamics properties. This software has many choices for prescribed thermodynamics properties. According to the analysis, it is known that the more ethane content in…

Gas cooler is one of the important components in CO2 refrigeration system and it must be designed properly. Conventional mathematical modeling used in designing heat exchanger have some drawbacks when the working fluid has large variation on its thermo physical properties. This paper discusses detail modeling and designing one of heat exchanger types which takes into account unique characteristic of CO2 as refrigerant. The mathematical model is then validated by experimental data. The comparison shows that the model predicts gas cooler performance within 2% maximum deviation. The principles…

This paper presents drum brakes thermal stress analysis for 6 ton truck capacity, due to friction between shoe and drum for two leading shoe brakes type. The mechanical and thermal loading are analyzed for various road conditions such as straight path, curved, and downhill path, with various value of deceleration. Based on the transient heat transfer, the drum temperature distribution are calculated for various deceleration and braking time period. Using finite element techniques, the thermal stressses are obtained and the results are compared to the actual failures evidences of brake drums.…

Pump as Turbine (PaT) tested from mixed flow pump type with 250 mm bore diameter, and impeller tip has a minimum modification by rounded the blade, which could improve the efficiency of 2% to 6%. The modification is done by rounded the impeller tip with 2 mm radius. Tested Pump as Turbine at 1000 rpm has an efficiency about 82% and 10 kW power output. The best power produced by 250 mm bore Pump as Turbine is 25 kW at the 75% efficiency. The 15 meters head may have the runaway speed of the Pump as Turbine on asymptotic level at 2500 rpm. The pump as turbine could utilized as Micro Hydro Power…