Showing papers on "Heat capacity rate published in 1971"

Heat transfer apparatus with improved heat transfer surface

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 thus 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.

High heat flux 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 transfer apparatus with immiscible fluids

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 thus 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 1000 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.

The Heat Pipe

Abstract: Publisher Summary This chapter classifies and evaluates the comprehensive literature collection composed of publications, papers presented at meetings, and reports of varying nature that appeared during the period from 1964 through midyear 1970 on heat pipe technology and on related topics. In the operation of a heat pipe, thermal energy is transferred from the evaporator to the condenser by continuous mass cycling and phase change of a suitable working fluid. In a heat pipe, the working fluid is continuously cycled by the surface tension forces of the fluid itself. It is this unique method of mass transfer that has both stimulated a growing interest in the heat pipe and has also proved to be one of the major impediments for a successful heat pipe operation. Theoretically, the heat pipe may be applied to almost a limitless number of thermal transport problems, which in general, can be subdivided into four broad topical categories depending on the particular feature of a heat pipe that is to be exploited. These areas of possible application are: (1) temperature flattening, (2) source–sink separation, (3) heat flux transformation, and (4) constant flux production.

Heat Transfer in Rocket Engines.

Abstract: : In the first part of this book the various basic heat transfer processes are considered, -- simple convective heat transfer from hot gases to the engine walls under various conditions, radiation heat transfer, and coolant heat transfer processes. This part is followed by one describing the various methods of cooling used in liquid propellant rocket engines, such as regenerative, film, ablation and radiation cooling. The final part concerns the properties of materials that will have to be known by the engine designer, from the transport properties of the hot combustion gases to those of the materials from which the engine will be constructed. Emphasis was placed on presenting simple methods for calculating the magnitude of heat transfer rather than providing the most modern and rigorous theories, particularly in the field of developing boundary layers. (Author)

Modular heat pump

Abstract: A heat pump assembly including multiple modular heat exchange units associated with a single refrigerant compressor motor unit with each heat exchange module including two heat exchange units which are alternatively and selectively employed as an evaporative heat exchange unit or a condenser heat exchange unit. One heat exchange unit in each module being associated with an ambient air circulating fan for use of the air as a heat exchange medium and the other heat exchange unit in each module associated with a liquid circulating pump system so that the liquid is used as a heat exchange medium.

Fuel cell heat and mass plate

Abstract: A novel method and apparatus is provided for controlling heat and mass inventory in a fuel cell. Heat and mass, e.g. water, generated in the cell are removed by heat transfer and capillary action.

Optimum control of heat exchangers with internal heat generation

Abstract: This paper investigates the optimum control of a heat exchanger having internal heat sources from a reference steady state to a desired value. Both the wall and coolant are treated as distributed-parameter systems. Under certain constraints inherent in the operating conditions and physical limitations of the heat exchanger, the control function of the system, i.e. the heat generation rate which minimizes the deviation of the temperature distribution from an assigned pattern at a given time, is found through the use of a linear programming method. The effects of physical parameters on the optimal control function and the temperature response and distribution are examined. Experimental results are presented which compare favorably with the theoretical analysis. Heat exchangers to which these results apply include the electrical heater, a chemical reactor in which a chemical reaction occurs within the solid walls and a heterogeneous nuclear reactor.

A General Purpose Fluid Flow Temperature Controller

Abstract: Fluid flow temperature controllers may be used as general purpose laboratory instruments if sufficient flow rate, control flexibility, and ease of design and fabrication are provided. Performance of 220°C/min slew rate and ±0.25°C dead band over the range −180 to 90°C is readily attainable from the instrument with nitrogen gas flows of 60 liters/min when liquid nitrogen is used as heat sink and boiling water as heat source.

High temperature heat transfer equipment

Abstract: Various alternative methods of high temperature heat transfer in the range of 300 to 750 F, such as direct firing, forced circulation of heat transfer fluids such as water, oil, Therminol, Dowtherm and other fluids are outlined. Advantages and disadvantages of each are discussed. Important considerations include design of heaters, temperature uniformity, heat transfer rates, safety precautions, hardware required, control sequences, fluid degradation and velocities.

Heat Transfer by Direct Flame Contact Fire Tests. Phase I

Abstract: : A laboratory study of the rate of heat transfer by convection and radiation to an object in direct contact with a flame was undertaken. The purpose was to devise a simplified mathematical procedure for computing the total heat transfer under these conditions based on these measurements. Another object of this work was to obtain sufficient information to design full scale field tests which can be used to test the validity of the mathematical model and the heat transfer rates as obtained in the laboratory. (Author)

Mathematical modeling of high and low temperature heat pipes

Abstract: Following a review of heat and mass transfer theory relevant to heat pipe performance, math models are developed for calculating heat-transfer limitations of high-temperature heat pipes and heat-transfer limitations and temperature gradient of low temperature heat pipes. Calculated results are compared with the available experimental data from various sources to increase confidence in the present math models. Complete listings of two computer programs for high- and low-temperature heat pipes respectively are included. These programs enable the performance to be predicted of heat pipes with wrapped-screen, rectangular-groove, or screen-covered rectangular-groove wick.

Evaluation of specific heat flows in an experimental installation by measuring surface temperature

Abstract: 1. The suggested method for determining specific heat flows requires a minimum number of known parameters and a minimum amount of work in processing experimental results. 2. The method is suitable for counting from the beginning of the process τ=0, and this is important in the case of short-term experiments. 3. It has been shown that local heat emission coefficients (mean with respect to time) can be determined by measuring the surface temperature of plates.