Showing papers on "Micro heat exchanger 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.

Heat transfer in a cylindrical cavity

Abstract: An analytical solution is developed to describe the unsteady-state heat transfer to a cylindrical cavity with circulating flow induced by a moving wall. The previously derived velocity field at low Reynolds numbers is incorporated into the energy equation, and the case of heat transfer to a fluid segmented by highly conducting plugs flowing in a tube with constant wall temperature is considered. Calculations of temperature distributions, average temperatures, and heat transfer coefficients as functions of time and Peclet number are presented for a specific cavity geometry, and the degree of enhancement in heat transfer caused by the recirculating flow is determined.The methods developed in this study may be useful in obtaining analytical solutions to a variety of closed-streamline heat and mass transfer problems with known velocity fields.

Analysis of Heat Exchangers for Dilution Refrigerators

Abstract: Numerical calculations of the behavior of dilution refrigerator heat exchangers are discussed and some results for both discrete and continuous exchangers are presented. It is shown that thermal conductance along the stream is negligible for a typical continuous exchanger of the coaxial tube type, but becomes a dominant feature of a typical discrete exchanger operating below about 50 mK and degrades the performance considerably. A simple design change can be made that reduces the conductance along the liquid and improves the performance of such an exchanger. A simple means of determining whether conductivity is important in either continuous or discrete exchangers is given.

Cooling apparatus for heat exchangers

Abstract: To improve the coefficient of heat transfer between the surfaces and the heat exchange media of heat exchangers, such as automobile radiators, steam condensers, and steam boilers. Conductive probes or conductors are energized with a low power, low current high DC potential and spaced from the surfaces a distance slightly greater than the distance at which arcing occurs while the surfaces are grounded to generate an electrostatic field.

The feasibility of electrohydrodynamic heat pipes

Abstract: The effect of a nonuniform electrostatic field on insulating dielectric liquids in heat pipes was studied. Topics discussed include the theory of operation, design criteria, and evaluation of optimal design features. It is concluded that the electrodynamic heat pipes offer advantages that must be weighed against the disadvantages in order to arrive at a proper assessment of their value in solving heat transfer problems.

Low temperature heat transfer in a plate-fin type heat exchanger

Abstract: Considerable amounts ofcopper and its alloys are employed in the manufacture of heat exchangers for low tempera ture refr igerat ion equipment In recent yea r s , c h r o m e nickel steels are being used for this purpose From the standpoint of compactness , minimum metal volume, low hydraul ic res is tance , and small loss of the cooling effect to the surroundings, plate-fin type heat exchangers descr ibed below offer considerable promise In the following, the heat t r ans fe r cha rac te r i s t i c s of these heat exchangers wi!l be discussed The welding of the fins with the p r imary heat t r ans f e r sur faces (plates) in these leads to a large increase in the total surface Compared to the conventional shel l -and-tube type exchangers the s u r face of a plate-f in type exchanger is nine t imes g rea te r on a unit volume basis Depending on the number and thickr, ess of the fins in each cavity, and also on the configuration of and the distance between the individual cavities, it ranges f rom 900 to 1800 m 2 / m 3 As a f ract ion of the secondary surface (fins) this comes to 050-090

Analytical and Experimental Studies of Compact Wire-Screen Heat Exchangers

Abstract: A compact heat exchanger should possess high effectiveness while satisfying the condition of compactness with respect to its internal and/or external volumes. A compact heat exchanger consisting of a large number of randomly stacked wire-screen discs attached to the inside of a tube, referred to as a matrix heat exchanger (see Fig. 1), offers advantages of compactness, no leakage problems, and simplicity of construction.

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.

Designs of the New Type Plate Heat Exchangers and their Heat Transfer Characteristics

Abstract: 前報までに得られた知見にもとづき, 新しい形状の伝熱板からなるプレート型熱交換器の開発を試みた。流路が二次元的な単純波型プレートで伝熱係数が極大を示すもの1種類と三次元的な流路をもつ多点接触の傾斜波型プレート6種類を試作した。いずれの伝熱板もそのプレス型の機械加工は容易であり, 前者の伝熱特性は前報までの知見をほぼ満足し既存の伝熱板にくらべ優れていることを確認した。後者のプレートは多点接触の構造をもち流体の高い圧力にも耐える特徴を有しており, 傾斜角度および波の間の距離の伝熱係数におよぼす影響を検討し, 好適なプレート形状を決定した。

Heat-exchanging method and apparatus

Abstract: Water is heated in a furnace at slight overpressure to saturation temperature and is thereupon discharged in a flash evaporator to form a vapor phase and a liquid phase. The gaseous phase is employed to heat one or more fluids in one or more first heat exchangers, and the liquid phase is used to heat one or more fluids in one or more second heat exchangers. Cooled liquid phase is pumped back into the furnace, together with the condensed vapor phase. The heating action in the furnace is regulated in dependency on the rate at which the vapor phase must be evacuated from the flash evaporator to maintain the pressure therein at exchangers. constant value, and the rate at which the liquid phase is caused to flow through the second heat exchanger or exchangers is a function of temperature in such heat exchangers.