Showing papers on "Micro heat exchanger published in 1977"
TL;DR: In this article, a heat exchanger design method for fixed or for minimum irreversibility (number of entropy generation units N/sub s/) is presented, in which the amount of heat transferred between streams and the pumping power for each side become outputs of the N/Sub s/ design approach.
Abstract: The thermal design of counterflow heat exchangers for gas-to-gas applications is based on the thermodynamic irreversibility rate or useful power no longer available as a result of heat exchanger frictional pressure drops and stream-to-stream temperature differences. The irreversibility (entropy production) concept establishes a direct relationship between the heat exchanger design parameters and the useful power wasted due to heat exchanger nonideality. The paper presents a heat exchanger design method for fixed or for minimum irreversibility (number of entropy generation units N/sub s/). In contrast with traditional design procedures, the amount of heat transferred between streams and the pumping power for each side become outputs of the N/sub s/ design approach. To illustrate the use of this method, the paper develops the design of regenerative heat exchangers with minimum heat transfer surface and with fixed irreversibility N/sub s/.
313 citations
129 citations
TL;DR: In this paper, an analysis of laminar flow and heat transfer in channels whose walls are interrupted periodically along the streamwise direction was made, and the basic heat transfer and pressure drop results were employed to investigate whether an interrupted-wall channel experiences an augmented heat transfer rate compared with that for a parallel plate channel.
Abstract: An analysis has been made of laminar flow and heat transfer in channels whose walls are interrupted periodically along the streamwise direction. Such channels are frequently employed in high-performance compact heat exchangers. Numerical solutions of the mass, momentum, and energy conservation equations yielded local heat transfer and pressure drop results. These results were obtained for a range of Reynolds numbers and for several values of a dimensionless geometrical parameter characterizing the streamwise length L of the individual plate segments which make up the interrupted walls. The Prandtl number was fixed at 0.7 for all the calculations. The basic heat transfer and pressure drop results were employed to investigate whether an interrupted-wall channel experiences an augmented heat transfer rate compared with that for a parallel plate channel. For conditions of equal heat transfer surface area and equal pumping power, appreciably higher heat transfer rates prevailed in the interrupted-wall channel for a wide range of operating conditions. The augmentation was especially marked for relatively short channels and high Reynolds numbers. The results also demonstrated the existence of a new type of fully developed regime, one that is periodic. At sufficiently large downstream distances, the velocity and temperature profiles repeat their values at successive axial stations separated by a distance 2L and, in addition, the average heat transfer coefficient for a plate segment takes on a constant value.
80 citations
Patent•
30 Jun 1977
TL;DR: In this paper, a heat transfer fluid (HTF) is heated by direct contact with the hot geothermal brine in cocurrent flow through a series of flash stages which are maintained at successively lower pressures so that the HTF is vaporized in each stage.
Abstract: A method for producing mechanical energy from geothermal brine in which a heat transfer fluid (HTF) is heated by direct contact with the hot geothermal brine in cocurrent flow through a series of flash stages which are maintained at successively lower pressures so that the HTF is vaporized in each stage. A working fluid is countercurrently flowed through the series of flash stages in indirect heat exchange with the vapor produced in each stage so that the vapor is condensed in each stage and the working fluid is progressively heated as it passes through the series of flash stages. The heated working fluid is utilized in a heat engine for the production of mechanical energy.
34 citations
TL;DR: In this paper, the authors examined the effects of deviating from the first two assumptions and presented a new solution to the third assumption, which has not always been fully recognized, which is that within one baffle crossing the shell fluid temperature change is small with respect to its overall change, (that is, number of baffles is large).
Abstract: The derivation of the mean temperature difference in heat exchangers is based on a number of assumptions or idealizations, the most important ones being that the heat transfer coefficient is constant throughout the exchanger; that the temperature of either fluid is constant over any cross section of its nominal path, that is, complete mixing, no stratification or bypassing; and that an additional assumption for shell and tube exchangers, which has not always been fully recognized, is that within one baffle crossing the shell fluid temperature change is small with respect to its overall change, (that is, number of baffles is large). In actual exchangers, any of the above assumptions are frequently subject to various degrees of invalidation. This paper examines the effects of deviating from the first two assumptions and presents a new solution to the third.
34 citations
Patent•
10 May 1977
TL;DR: In this article, an approach and method for cleaning the heat exchanging surfaces of the heat transfer plates of rotary regenerative heat exchangers comprising low to medium pressure gas and/or steam operated nozzles of the injection type having injection tubes for moving by suction ambient heat exchanging gas or air into the interspaces between the Heat transfer plates.
Abstract: Apparatus and method for cleaning the heat exchanging surfaces of the heat transfer plates of rotary regenerative heat exchangers comprising low to medium pressure gas and/or steam operated nozzles of the injection type having injection tubes for moving by suction ambient heat exchanging gas or air into the interspaces between the heat transfer plates. The nozzles may be designed as supersonic nozzles, especially Laval nozzles.
24 citations
Patent•
05 Jan 1977
TL;DR: In this article, an improved system of transferring heat energy from a high temperature fluid to a low temperature fluid is described, where a countercurrent heat exchanger is employed in which heat transfer fluids undergo one or more thermodynamic transitions at various pressures by employing conventional heat exchangers having additional components.
Abstract: An improved system of transferring heat energy from a high temperature fluid to a low temperature fluid is described. A countercurrent heat exchanger is employed in which heat transfer fluids undergo one or more thermodynamic transitions at various pressures by employing conventional heat exchangers having additional components. It has been determined that by employing this system of the present invention under a critical choice of design parameters, a substantially greater amount of heat energy can be transferred per unit area of the heat exchanger than was possible by conventional techniques.
18 citations
18 citations
18 citations
Patent•
14 Nov 1977
TL;DR: A heat pipe heat exchanger has a plurality of heat pipes which are interconnected so as to permit fluid communication between the pipes at least during charging so that the heat pipes may be simultaneously filled with heat transfer fluid as discussed by the authors.
Abstract: A heat pipe heat exchanger has a plurality of heat pipes which are interconnected so as to permit fluid communication between the pipes at least during charging so that the heat pipes may be simultaneously filled with heat transfer fluid.
TL;DR: In this article, heat transfer and wall friction parameters have been obtained numerically to demonstrate the effects of mixture composition and gas property variation for heating or cooling in regenerative heat exchangers of such cycles; the situation is modeled by laminar flow through short ducts with constant wall heat flux.
Patent•
10 Nov 1977TL;DR: A fluid circulation system for heat exchangers has two groups of tubes through which primary and secondary fluids flow, the tubes of one group being interdigitated with the tubes from the other group, and a heat transfer material interposed between the two groups, whereby heat is transferred from the primary fluid through the heat transfer materials to the secondary fluid as mentioned in this paper.
Abstract: A fluid circulation system for heat exchangers having two groups of tubes through which primary and secondary fluids flow, the tubes of one group being interdigitated with the tubes of the other group, and a heat transfer material interposed between the two groups of tubes, whereby heat is transferred from the primary fluid through the heat transfer material to the secondary fluid. A shell forms a closure around the tubes and the heat transfer material, and the shell has tertiary fluid inlet and outlet means. Openings in the heat transfer material form passageways through which the tertiary fluid can flow from the inlet means, through the heat exchanger, to the outlet means. Piping connects the tertiary fluid outlet means to the tertiary fluid inlet means, forming a complete cycle. Installed in this piping is a heat removal system. If the secondary fluid flow is interrupted, the tertiary fluid provides a redundant means by which the heat of the primary fluid can be removed from the heat exchanger. Monitoring means can be inserted into the piping, to detect any leakages which may occur in the primary and secondary tubes. Condensers or desiccating material can be installed in the heat removal means to remove any liquids which may leak into the tertiary fluid. Additionally, if the tertiary fluid is a gas or vapor, a turbine can be inserted into the piping and the tertiary fluid's power utilized to provide energy to power the compressor or pump which is circulating the tertiary fluid. In an emergency, this turbine can be connected to an electrical generator and provide emergency power to the rest of the plant.
TL;DR: In this article, an iterative technique was used to calculate the local heat transfer coefficient without iteration in the corresponding cases of combined radiation and convection for convective cooling or heating of liquids.
Patent•
22 Jun 1977
TL;DR: In this article, a heat exchanger where the hot and cold sides are arranged in side-by-side relationship, both sides being connected to a reactor by properly valved pipes, and means providing for a forward flow with reactor influent flowing through one side to the reactor and thermally conditioned liquid exiting from the reactor through the other side.
Abstract: A heat exchanger wherein the hot and cold sides are arranged in side-by-side relationship, both sides being connected to a reactor by properly valved pipes, and means providing for a forward flow with reactor influent flowing through one side to the reactor and thermally conditioned liquid exiting from the reactor through the other side. Valves are selectively operable to reverse this flow. One form of the invention utilizes a pair of heat exchangers utilizing a third heat transfer medium.
TL;DR: Huq et al. as mentioned in this paper proposed an optimal solution for convecting fin with variable thermal conductivity, and discussed the effect of internal heat generation on heat transfer in thin fins.
Dissertation•
01 Jan 1977
TL;DR: In this paper, the authors present an approach to solve the problem of the problem with the use of a set of algorithms from the Massachusetts Institute of Technology Dept. of Mechanical Engineering.
Abstract: Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering.
TL;DR: The mass transfer analogue method, used previously to measure heat transfer coefficients in a single internal compartment of a small cylindrical shell-and-tube heat exchanger model, has been used to study the case where clearances exist between shell and baffle as discussed by the authors.
27 Jun 1977
TL;DR: In this paper, an investigation was made into the effective application of porous heat exchangers of cylindrical shape through which fluid passes axially, and the conclusion derived was that the best thermal efficiency can be reached by the use of porous material with a large heat-exchanger surface, a high radial and low axial thermal conductivity, and a small radius of the heat exchanger operating at lower flows of cooling agent.
Patent•
08 Mar 1977
TL;DR: In this paper, assisted flow ventilation heat exchanger systems with a fan assisted flow are described. But the authors focus on the distribution of the heat exchangers in such a way that they fulfill a distributor function for the fan, i.e., they provide an angular momentum to the cooling fluid which is such as to counteract the angular momentum provided by the fan.
Abstract: The invention relates to assisted flow ventilation heat exchanger systems which comprise heat exchangers disposed at the bottom of a cooling tower with a fan assisted flow and wherein the exchangers are disposed in such a way that they fulfill a distributor function for the fan, ie they provide an angular momentum to the cooling fluid which is such as to counteract the angular momentum provided by the fan
TL;DR: In this article, an exact solution to the problem of thermal entry region heat transfer in a circular tube with an arbitrary circumferential wall heat flux for pseudoplastic fluids using the power law constitutive model was obtained.
Abstract: An analysis is performed to obtain an exact solution to the problem of thermal entry region heat transfer in a circular tube with an arbitrary circumferential wall heat flux for pseudoplastic fluids using the power law constitutive model. The solution is expanded in a power series form, with expansion coefficients and related constants obtained numerically. A simple result is presented for a cosine heat flux distribution around the periphery of the tube which illustrates the simultaneous influence of circumferential wall heat flux variation and non-Newtonian fluid behavior on heat transfer.
TL;DR: In this article, a simple hypothesis based upon the two-phase theory of fluidisation is proposed as an alternative to the present, inaccurate empirical approach, and the prediction of the fluidising velocity at which the heat transfer coefficient maximum is obtained is considered.
Patent•
14 Jul 1977
TL;DR: In this article, a heat exchanger is embedded in the soil, and is connected by pipes to a sun collector which consists of a heat exchange (HE) possessing a glass plate (3).
Abstract: A heat exchanger (1) is embedded in the soil, and is connected by pipes (2) to a sun collector which consists of a heat exchanger (4) possessing a glass plate (3). The collector is positioned roughly at right angles to the main impact of the sun's rays. The size of the heat exchangers (1,4) can depend on circumstances. Additional heat exchangers can be provided. If the soil is situated on a natural incline, the collectors can be positioned to suit the slope and the water is rotated by gravity. When the ground is level, the collector (3,4) must be higher than the heat exchanger (1). In this case it is necessary to have a pump in one of the pipes (2).
TL;DR: In this paper, the problem of heat transfer between parallel plates can be solved in terms of transport relaxation eigenfunctions, and the particle distribution function and the total heat transfer in the Knudsen case are exactly expressed by integrals over the interfacial scattering kernel occurring in the new scheme.
Abstract: Within the framework of boundary conditions recently developed for the linearized Boltzmann equation 1 the problem of heat transfer between parallel plates can be solved in terms of \"transport- relaxation eigenfunctions\". The particle distribution function and the total heat transfer in the Knudsen case are exactly expressed by integrals over the interfacial scattering kernel occurring in the new scheme. A detailed discussion of the general case gives an exact formula and sign statement for the temperature jump at parallel plates. An approximation, which encompasses v. Smoluchowski's approach, lies at hand. This approximation is also readily confirmed by a moment method.