Digital computer simulation of complex radiant heat load.
Abstract The exchange of radiant heat between an absorber and a variety of radiators in its surroundings is capable of calculation by digital computer. When the absorber is characterized as a black body, the calculated results may represent the maximum potential radiant heat load upon a man occupying the absorber location. Calculations of heat exchange for a matrix of absorber locations within a work space permits the construction of isopleths of heat load in that work space; this may be done for any elevation of interest. The contribution made by each individual radiator to the heat load on absorbers at the various locations may be obtained. Repeated computer runs using simple changes in input data may be used to simulate various alternatives for control of radiant heat exposures. Use of a digital computer permits mathematical assessment of radiant heat exchange problems for which manual calculations would be prohibitively time consuming and costly.
Calculation of Complex Radiant Heat Load From Surrounding Radiator Surface Temperatures
Abstract A method for calculating the radiant heat exchange between an absorber and individual radiating components in its surroundings is reported. Radiator surface temperatures, ambient and absorber temperatures, and configuration factors for radiating components in the surroundings are used in the customary radiant heat exchange formulae. Simplified methods for calculating or estimating configuration factors for radiators of various shapes solely from angles, subtended at the absorber by the radiators are presented. The method has been verified in the laboratory under controlled conditions and has been used to advantage in the field studies. The method has advantages over the globe therometer method in certain applications.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.