Showing papers on "Heat capacity rate published in 1970"

Heat exchange methods and apparatus

Abstract: Heat exchange apparatus and methods in which liquids having different phase change characteristics absorb heat from a relatively hot gas at one location and give up the heat to a relatively cool gas at a second location.

Heat Transfer in Compression-Ignition Engines: First Paper: Heat Transfer in a Quiescent Chamber Diesel Engine

Abstract: Instantaneous and mean values of heat transfer at various positions in the combustion chamber were obtained, by means of surface thermocouples, for different loads and speeds and compared with those obtained theoretically from synthesized cycle calculations. The results show that the usual model of homogeneity in the cylinder is inadequate for heat transfer calculations. Peak rates of heat transfer when in the vicinity of a fuel spray were comparatively little dependent upon load or speed. At the periphery of the combustion chamber the mean heat transfer rates were appreciably lower than to the cylinder head and piston and the rapid rise in instantaneous values occurred appreciably later. The results all suggest the need for a more realistic model based upon the geometry and penetration of the fuel sprays.

Heat link, a heat transfer device with isolated fluid flow paths

Abstract: A heat transfer device, defined here as a heat link, having a capillary vaporizer adjacent a heat source, transfers heat to a heat sink by vaporization and condensation of a heat transfer fluid within the device. A first passage is provided for conveying vapor from the capillary vaporizer to the heat sink. Another passage which is essentially a continuation of the first passage, conveys condensed liquid from the heat sink to the vaporizer, thus allowing the distance that the liquid must flow through capillary material to be quite short. Contact of the returning liquid with the surface of the vaporizer is assured by providing means for maintaining the temperature of the liquid in the return line at a sufficiently low temperature that any vapor will condense; or, alternatively, by having means for extracting any vapor formed in the returning liquid. In this manner, the heat link operates with high heat flux without any substantial resistance to liquid flow through a long capillary flow path. By this replacing almost all of the liquid return wick, with its high resistance to fluid flow, of heat pipes with a low flow resistance liquid passage or conduit, the heat flux capacity of the heat link is greatly increased over that of the heat pipe while the quantity of porous material used and the heat link weight are considerably reduced so that a heat link typically has 10 to 1,000 times the heat flux capacity of a heat pipe having the same weight. "Boosted" embodiments of the heat link employing additional means for circulating the fluid, such as vapor jet pumps, powered at least in part by vapor from the capillary vaporizer, are also described. Some "boosted" heat links are capable of handling heat fluxes in the multi-megawatt range while having no moving parts except for check valves and the fluid itself.

Segmented heat pipe

Abstract: An improved heat pipe capable of conveying a greater heat flux than a conventional heat pipe is provided in practice of this invention. A heat pipe transfers heat from a heat source to a heat sink in the form of latent heat of vaporization of a fluid within the heat pipe. Hot vapor transfers heat from the heat source to the heat sink. Condensed liquid is returned from heat sink to the heat source through porous capillary material due to surface tension forces. The heat flux obtainable is limited by the available flow of returning liquid. In the improved heat pipe, the flow paths for liquid and vapor are serially segmented by impermeable barriers transverse to the direction of heat flow so that the distance of liquid flow in each segment is minimized. In zero gravity the heat flux obtainable is approximately proportional to the number of serial segments N into which the heat pipe is divided, that is, if the heat is transferred serially through N segments approximately N times the heat flux is possible as compared with a conventional heat pipe of the same overall dimensions. When operating against a gravity head, the maximum heat flux is about N2 times the heat flux of a conventional heat pipe. Thus a heat pipe segmented into 10 serial segments has approximately 10 to 100 times the maximum heat flux capacity of an unsegmented heat pipe of the same cross section and total length.

Heat pipe with dual working fluids

Abstract: In a heat pipe containing a main working fluid that normally freezes under low heat loads, an auxiliary working fluid is provided that, although being less efficient than the main working fluid, nevertheless remains liquid at low heat loads when the main working fluid freezes, so as to sustain heat pipe action.

Semiconductor cooling system and method

Abstract: In a method and a system for cooling semiconductors submerged in a liquid, the semiconductors, one or several, are, together with the liquid, arranged in a tank connected to a heat exchanger. The heat transport from the semiconductors takes place by the latent heat of vaporization of the liquid, transferring the heat to the heat exchanger. The pressure in the system is substantially nonvarying.

Heat exchange units and heating systems employing such units

Abstract: Heat exchange units of the type in which a fluid heat transfer medium is circulated in counterflow relationship through independent flow paths. Heating systems employing such heat exchange units.

Electric versus Steam Energy for Pipe-Line Tracing

Abstract: Under no-flow conditions, the energy required to maintain a given temperature on a pipe line is directly proportional to the product of the line temperature above ambient and the time that the temperature is maintained. Since outside ambient temperature varies as a sine curve about the average temperature, the amount of heat required is also continuously changing. On a line traced to prevent freezing manually, controlled, or uncontrolled, steam will expend over 700 percent more energy to maintain the temperature than will electric tracing. With flow in the pipe, the heat wasted by steam can be even greater since the flowing material acts as a heat sink. Since the flow conditions affecting heat loss vary greatly, each installation must be calculated separately. It is quite possible that a steam tracer will expend energy at its maximum rate under conditions that would not require any heat. Steam tracing is more efficiently used on lines requiring a temperature approaching that of the tracing steam.

Fluid temperature controller

Abstract: Apparatus for controlling the operating fluid temperature in a closed fluid circuit including a torque converter and a heat exchanger in which the heat generated in the torque converter fluid varies widely and in which part of the fluid bypasses the heat exchanger. An electrical signal is generated whose amplitude is dependent on the temperature of the fluid leaving the heat exchanger which signal is modified to reflect the rate of change of this temperature. A second signal is generated, the amplitude of which is dependent on the temperature of the fluid bypassing the heat exchanger and this signal is modified to reflect the percentage of the fluid bypassing the heat exchanger. These signals are combined and the resulting signal is compared at preselected intervals to a standard signal representing the desired fluid temperature to control the coolant flow through the heat exchanger.

Marine reheat cycles and systems evaluation

Abstract: In light of recent improvements in steam propulsion resulting from the application of the reheat cycle, it is the purpose of the paper to present general and accurate comparative data, to aid others in the proper application of reheat and to evaluate its gains. Schematic engine room arrangements for a symmetrical plant as well as one designed for improved economics are presented for possible application on twin-screw, high-utilization, fast-turnaround vessels. Various methods for specifying reheat performance are reviewed and reasons for a new method are given. A heat rate method is proposed and developed to help inprove standards of calculation and specification. Heat rate factors are provided on most engine room components to allow trade-off studies. Typical all-purpose fuel rate curves for five cycles are shown for 30,000 to 200,000 shp. Representative heat balance data are given to allow the marine designers to size or specify components by interpolation on a preliminary basis.