Showing papers on "Heat capacity rate published in 1982"

Calculations of the Heat Release Rate by Oxygen Consumption for Various Applications

Abstract: The calculation of heat release rate by oxygen consumption is based on the assumption that all materials release approximately the same amount of heat per unit mass of oxygen consumed. This technique is now being employed to determine the heat release rate of materials in various heat release rate calorimeters. Other uses include the heat release rate of assemblies in the fire endurance furnaces and the total heat release rate in room fire tests. These different applications lead to different experimental procedures which require different formulas. The experimental choices or constraints include open or closed systems, paramagnetic or high temperature oxygen analyzers, CO analyzers or CO traps, and the use of a gas burner whose heat release rate must be deducted from the total. Various assumptions about CO levels in the exhaust duct and vitiation and humidity in the incoming air are made. General formulas for the heat release rate by oxygen consumption are developed in this paper from which the formulas for specific applications can easily be derived.

intrinsically irreversible heat engine

Abstract: A class of heat engines based on an intrinsically irreversible heat transfer process is disclosed. In a typical embodiment the engine comprises a compressible fluid that is cyclically compressed and expanded while at the same time being driven in reciprocal motion by a positive displacement drive means. A second thermodynamic medium is maintained in imperfect thermal contact with the fluid and bears a broken thermodynamic symmetry with respect to the fluid. the second thermodynamic medium is a structure adapted to have a low fluid flow impedance with respect to the compressible fluid, and which is further adapted to be in only moderate thermal contact with the fluid. In operation, thermal energy is pumped along the second medium due to a phase lag between the cyclical heating and cooling of the fluid and the resulting heat conduction between the fluid and the medium. In a preferred embodiment the engine comprises an acoustical drive and a housing containing a gas which is driven at a resonant frequency so as to be maintained in a standing wave. Operation of the engine at acoustic frequencies improves the power density and coefficient of performance. The second thermodynamic medium can be coupled to suitable heat exchangers to utilize the engine as a simple refrigeration device having no mechanical moving parts. Alternatively, the engine is reversible in function so as to be utilizable as a prime mover by coupling it to suitable sources and sinks of heat.

Process for increasing the heat flow density of heat exchangers working with at least one high-velocity gaseous medium, and a heat exchanger apparatus for undertaking the process

Abstract: A method and apparatus are disclosed for increasing the heat flow density of heat exchangers having at least one gaseous fluid flowing therethrough at a high velocity. In one form of the method, which may be used in motor vehicles, the energy for the acceleration of the gaseous fluid is taken from the exhaust gases of an internal combustion engine. In this respect, an exhaust gas heat exchanger used for vehicle interior heating, or a heat exchanger used for cooling the engine coolant, may be used. In order to increase the energy content of the exhaust gas, the exhaust gas undergoes a pressure build-up. The waste heat of the exhaust gas may thus be used at low engine loads, with a relatively low need for engine cooling and a relatively high need for interior heating, in order to increase the heat flow density at the exhaust gas heat exchanger for vehicle heating. While at high engine loads with a relatively small need for interior heating energy, but with a high need for engine cooling, the exhaust gas may be used for increasing the heat flow density in the radiator. Preferably, the heat exchanger system for heating the vehicle includes a selectively operable pressure build-up unit in the flow path for the exhaust gas.

Heat exchange system with space heating, space cooling and hot water generating cycles

Abstract: This invention pertains to a heat exchange system having a space heating, a space cooling and an independent water heating cycle. During the space heating and space cooling cycles a refrigerant is used to transfer heat by circulating between a condenser/evaporator and a heat exchanger, the refrigerant being evaporated and condensed in the process. During the independent water heating cycle a third heat exchanger is used to condense the refrigerant. The heat removed by this exchanger is used for the evaporating of the refrigerant. A fourth heat exchanger is provided for water heating. Either water pumped from an outside source or outside air may be used as a heat source and sink.

Apparatus and method for evaluating the performance of a heat exchanger

Abstract: A method and apparatus for evaluting the performance of a heat exchanger are described. Water is supplied to the heat exchanger at a known mass flow rate and temperature. The water is directed to traverse a flow path of the heat exchanger. The water is then heated and redirected into another flow path of the heat exchanger in heat exchange relation with the first flow path. The temperature change of the water over a flow path is measured to determine the performance of the heat exchange. The water flow rate and incoming water temperature may be fixed to make a single discharge temperature measurement sufficient to calculate heat exchager performance.

Hot-gas piston type engine

Abstract: An intermediate circuit is connected between the compression space acting as a first heat exchanger of the cylinder of a heat pump or a working machine and the water for industrial use or the burning space of an oil burner, the intermediate circulator comprising a second heat exchanger protruding within the water for industrial use. Through the utilization of an intermediate circulator with a gaseous or liquid auxiliary medium is possible to adapt the transfer of heat between the cylinder of the machine and the heat medium to the respective conditions which permits to increase the total efficiency.

Basic findings obtained from measurement of the combustion process

Abstract: The heat release of internal combustion engines decisively influences exhaust emissions, fuel economy, smoke and noise. Previously, however, the measurement methods were complicated and insufficiently accurate. Therefore heat release data were not often used. By means of an improved measurement and evaluation system it is now easier to determine the heat release with higher accuracy. The required combustion pressure diagram is recorded and then processed by means of a desk computer at the test stand. Because of the low calculation speed of desk computers, it is necessary to optimise carefully the algorithms in order to arrive at an acceptable computation time. To this end an approximative equation for the specific heat, a thermodynamic determination of the pressure diagram zero line and a simplified method of calculating the heat release are described, the use of which leads to an extremely short calculation time of about 5 seconds. This allows a quick evaluation of the rate of heat release directly at the test stand and so its immediate application in engine development. The kind of information which can be gathered from the rate of heat release is shown in some examples which compare typical results gained in an Otto cycle engine and three different direct injection diesel systems. The importance of determining the rate of heat release in unsteady operation is shown by the example of engine starting. (Author/TRRL)

Thermally powered heat transfer systems

Abstract: A thermally powered heat transfer system consisting of two closed heat transfer loops which share a compressor which is alternately powered by the refrigerants of the two loops. This system is powered by two heat sources having different temperatures of which the lower temperature heat source may be the heat within a structure to be cooled. An evaporator of the first loop located within the structure to be cooled is charged with a low boiling point refrigerant while an evaporator of the second loop is heated by a higher temperature heat source and is charged with a higher boiling point refrigerant. The heat sinks of the loops are at temperatures between those of the two heat sources. Controls are activated at the completion of each compressor stroke, or cycle, to alternately open and close valves which regulate vapor and liquid flows to cause the compressor to act with compressive force upon one or the other refrigerant vapor during each cycle of operation of the system to effect useful heat transfer.

Heat Transfer in Surface-Cooled Objects Subject to Microwave Heating

Abstract: Several investigators in microwave bioeffects research have exposed biological preparations to intense microwave fields, while at the same time cooling the sample with flowing water. We examine the heat transfer characteristics of this situation, to estimate the maximum temperature increase and thermal time constants that might be encountered in such an experiment. The sample is modeled as a uniform sphere, cylinder, or slab subject to uniform heating, which is located in an unbounded coolant flow. The heat transfer is determined by the Biot and Reynolds numbers (which reflect the geometry, fluid flow, and material thermal properties of the system) the temperature rise is governed by the heat conduction equation coupled with external convection. The results are expressed in terms of nondimensional quantities, from which the thermal response of a heated object of arbitrary size can be determined. At low coolant flow rates, the maximum temperature rise can be biologically significant, even for relatively small objects (of millimeter radius) exposed to moderate levels of microwave energy (with a SAR of ca. 100 mW/g). The results are valid also where the coolant is a gas or a liquid different from water, the only restriction being on the Reynolds number of the flow.

Device for passive downward heat transport - Design criteria and operational results

Abstract: A semi-continuous device for passive downward heat transport has been designed, built and operated. Heat is transported as latent heat of vaporization as in a heat pipe; the return of the liquid is obtained through the action of an energy accumulator containing an inert gas and charged by the vapour itself during the transport of heat. The capability of winning the difference in level is exchanged with a difference of a few degrees centigrade between evaporator and condenser. The laboratory device worked with a difference in level of 1. 7 m. Working under pressure, differences in level of 10 meters and more can be attained. A typical application can be the storage of heat available from solar collectors.

Non-intrusive thermal power monitor and method

Abstract: A non-intrusive thermal power monitor and method for determining the amount of sensible heat withdrawn from or added to a fluid stream flowing in a conduit by an unknown source includes a thermal power transfer device that supplies or removes a known amount of heat energy to the fluid in a conduit. First and second temperature sensors sense the temperature of the fluid stream across the thermal power transfer device, and this information is used to determine a heat capacity rate of the fluid in the fluid stream. Additional non-intrusive temperature sensors sense the temperature of the fluid stream as it passes through and across a thermal power sink or heat source and provides a temperature differential. These temperatures are processed in a control circuit, and the thermal power added to or extracted from the fluid stream is determined in the control circuit by multiplying the measured temperature differential by the heat capacity rate of the fluid stream.

Apparatus and method for heating and chilling concrete batch water

Abstract: Modular apparatus for providing heating and cooling to large quantities of water used in a concrete batch plant prior to mixing water and concrete is disclosed. The system typically operates from a water source such as a deep well (10) which water source may serve as either a heat sink or a heat source. In addition, there is a water storage tank (34) which holds water (36) which water can be either heated or cooled as necessary for the best results in mixing concrete. There is a multiplicity (26) of modular reversable heat pumps each of which has its heat exchanger (78, 88) connected in parallel such that modular units may be added or removed without destroying the integrity of the refrigerant system. Each of the modular units includes a source heat exchanger (88) and a storage heat exchanger (78). A gaseous refrigerant compressor (70) is also provided and operates in conjunction with a reversing valve (80) such that the direction of refrigerant flow through the heating exchanger (78) and (88) may be reversed while at the same time the direction of refrigerant flow through the compressor (70) remains the same. There is further included a refrigerant expansion means (130) which also operates in combination with a fluid flow reversing bridge (104) such that the flow of fluid through the expansion valve is always in the same direction, even though the flow of refrigerant fluid through heat exchangers may be reversed. There is also included circuitry (66) which monitors and controls the operation of the reversable modular heat pumps to maintain the temperature of the storage water (36) in tank (34) at within a preselected temperature range.

Indirect counterflow heat recovery system of the regenerative type for steam generators, gas turbines, and furnaces and engines in general

Abstract: A heat regenerator indirectly utilizes the hot gases exhausted by a furnace or engine to heat the air supply to it, through the use of heat transfer fluids which function as an efficient heat transfer medium to implementation of the counterflow and direct contact heat transfer principles.

Thermodynamic analysis of heat pipe operation

Abstract: Operation of heat pipes as closed thermodynamic multi-component systems is analyzed. The expressions are obtained for transported thermal energy in the dry, moist and superheated vapor as well as in supercooled fluid phase. Different thermodynamic operating conditions of heat pipes are compared with the experimental data. The exergy balance is used to obtain the expressions for the thermodynamic efficiency of heat pipes. The thermodynamic analysis of the efficiencies of a gas laser — heat pipe is given.

Hybrid heat pump

Abstract: The invention relates to a heat pump with compressor, in the thermodynamic system of which, solution is used. This way varying temperature conditions take place on the heat intake and heat discharge side. Provided that varying temperature system appears also on the demand side, adapting the heat pump of the invention accordingly, the specific cooling capacity may be several times that of the traditional cooling machines under identical temperature parameters. The "wet compression" worked out in the invention, results in further increase of the specific cooling capacity, as well as it makes the competetiveness of the heat pump according to the invention indisputable in such field as for instance deep freezing.

Method for measuring the production of heat by microorganisms, and device for carrying out the same

Abstract: The device for carrying out the method for measuring the production of heat by microorganisms contains a fermenter (1), in which the cultivation of microorganisms is carried out in a nutrient medium at a prescribed cultivation temperature. A calorimeter (12) is in thermal contact with the fermenter (1) and is used to measure the production of heat in terms of the magnitude of the thermal flux deriving from the culture mixture. Provided in the fermenter (1) is a heat source (16) which is provided with a control loop (17) for feeding heat into the fermenter. The heat is directed from the heat source (16) to the nutrient medium and the culture mixture in an amount corresponding to the quantity of heat which is consumed for the processes of heat and mass exchange in the fermenter (1) and is dissipated therefrom. In this case, during the stage of cultivating the microorganisms the quantity of heat supplied is changed in accordance with the change in the processes of heat and mass exchange with the aid of a control loop (17) which consists of a device (18) for measuring the viscosity of the culture mixture, which is electrically connected to an electric motor (8) of a stirrer (7) arranged in the fermenter, a transducer (19) for converting the viscosity variable into a performance variable of the heat source and which is connected in the input side to the output of the device (18), and a controller (20) for the output of the heat source, which is connected on the input side to the output of the transducer (19) and on the output side to the heat source (16). The device also contains a device (22) for maintaining the temperature of the environment outside the fermenter, which is constant or equal to the culture mixture, and excludes possible losses of a portion of the flow of heat stemming from the culture mixture due to the exchange of heat with this environment, and a heat exchanger (13), which is in thermal contact with the calorimeter (12) and has a device (14) by means of which the temperature of its working surface is kept constant.

Power generation plant which utilizes medium with low boiling point

Abstract: PURPOSE:To permit both the intermediate liquid medium used for recovering the exhaust heat from a heat source and the working gas medium used for driving a turbine to make natural circulation by means of the difference of density between the liquid and gas, by carrying out heat-exchange between both mediums, through a direct contact heat exchanger. CONSTITUTION:The intermediate liquid heat medium 2 which recovers the heat through a heat recovering apparatus 1 and the liquid working medium 3 which is liquefied in a condenser 5 are introduced under pressure by the gravity, into the lower part of a direct contact heat exchanger 8. Both mediums are formed into two-phase stream consisting of gas and liquid through the evaporation of the working medium 3 and introduced into a gas-liquid distributor 10, and the intermediate liquid medium 2 is returned into the heat recovering apparatus 1 by the action of gravitation. After driving a turbine 4, the gas working medium 3 is liquefied in a condenser 5 and returned into a heat exchanger 8 by the gravity.

Disposition of heat pumps

Abstract: is used in such an arrangement, in which the Unterkuh lungsenthalpie means of a second heat pump and the thereby obtained and raturniveau elevated to a higher tempering heat in addition to that of the first heat pump as useful heat is additionally discharged, is in the circulation of the working fluid of a first heat pump (1 , 5, 6, 8, 10) comprises a second heat pump (11 to 14) is inserted such that it directly causes a cooling of the liquid working fluid.

Test results of a medium temperature solar engine

Abstract: SYNOPSIS The results of a test programme of a completely fluorinated organic fluid solar engine at fluid temperatures around 250°C are Engine design characteristics. as deduced using the particular fluid properties are briefly described problems encountered in the preliminary test phase and relating to fluid losses, heat exchangers reduced performance and minor mechanical disturbances are illustrated together with the actions undertaken to improve the original engine behaviour. Detailed engine overall and components performance, as derived from a series of tests, carried out with a fuel fired heat source (simulating the actual solar heating loop) are presented. Engine efficiency, with reference to the net power output at the high speed shaft proved to be around 21%, at 250°C turbine inlet temperature which can be compared with 22.6% design value at the same temperature and with 23.6% original goal at 280°C top cycle temperature. The analysis of the heat transfer coefficients within the various heat exchan...

Motive power generator

Abstract: PURPOSE:To collect heat always at the maximum energy efficiency in a plant which generates power by use of sun heat or waste heat of a plant by integrating a plurality of heat accumulation tanks which differs in temperature of accumulated heat, in a heat collection loop and by selecting an appropriate one from those tanks according to condition of a heat source or so. CONSTITUTION:A heat collection loop is made up of a heat collector 1, three-way valves 11a and 11b, a steam generator 5, a heat accumulation tank unit 3, a heat medium circulation pump 4 and a bypass flow passage 40 which are properly connected to each other. The heat accumulation tank unit 3 consists of low and high temperature heat accumulation tanks 3a and 3b which differ in temperature of accumulated heat. A Rankine cycle 2 is formed by piping the steam generator 5, an expansion mechanism 6, a condenser 7 and a pump 8a. An optimum value of a temperature of heat medium at the inlet of the heat collector, determined according to temperature of open air and intense of solar radiation is shown by T0 and temperatures of heat accumulation tanks 3a and 3b are shown by T1 and T2. The three-way valves 12a and 12b are placed under change-over control as to select the low temperature heat accumulation tank 3a for T2>T0>T1 and select the high temperature heat accumulation tank 3b for T0>T2.

Heat-actuated heat pumping apparatus and process

Abstract: A heat actuated heat pumping apparatus and process having two working chambers to provide a Vuilleumier cycle for space conditioning. The working chamber volumes are in pressure communication with each other in the vicinity of intermediate thermal exchange means in each volume equalizing the pressure between the two working volumes with one module acting as the driver for the heat pumping action of the second module. Pressure communication may be maintained through a floating piston thereby providing two different intermediate heat rejection temperature levels resulting in a four temperature level Vuilleumier heat pump. The apparatus and process of this invention reduces mechanical complexity and improved thermal exchange in a heat pump system suitable for large air conditioning applications and hot water heating as well as small refrigeration and cryogenic applications.

Process and device for the thermal treatment of a liquid fuel.

Abstract: Liquid fuel is conducted from a storage container (1) through heat exchangers (6, 8, 10) by means of which the liquid fuel is transformed into a gaseous state of matter. The gaseous fuel is thereupon introduced into the utility chamber section (16) of the internal combustion engine. A heat exchanger (6) is heated by taking dissipation heat from the cooling fluid (18) of the internal combustion engine. In another heat exchanger (8) a quantity of heat is taken from the exhaust gases (19). Another heat exchanger (10) is heated by an accumulator (21) or a power generator (20), which are associated with the internal combustion engine. The heat exchangers (6, 8, 10) are in each case associated with a heat accumulator (7, 9, 11).

Solar heating unit and heat transfer apparatus

Abstract: A heating unit (10) transfers energy via vaporized working fluid exclusively. The unit operates at sub-atmospheric pressure and a unique heat transfer apparatus (84) is provided to serve as an energy absorber panel (12) and/or a heat exchange unit (44). Since vaporized working fluid is utilized to transfer energy several hundred times the amount of energy can be transferred per unit weight of working fluid as compared to systems which transfer energy via liquid working fluid. Thus, a minimal amount of working fluid can be utilized. The heating unit (10) is constructed so as to prevent the delivery of working fluid to the interior cavity (18) of the energy absorber panel (12) in response to the working fluid within the cavity (18) reaching a selected level. Vapor is conducted from a location in the cavity (18) above that selected level to the heat exchange unit (44). The working fluid is selected to boil at a sub-atmospheric pressure within the cavity (18) at a temperature which falls within a range from about 27° C. to about 99.5° C.

Heat Pipe Development for the SPAR Space Power System

Abstract: The SPAR space power system design is based on a high temperature fast spectrum nuclear reactor that furnishes heat to a thermoelectric conversion system to generate an electrical power output of 100 kW e. An important feature of this design is the use of alkali metal heat pipes to provide redundant, reliable, and low-loss heat transfer at high temperature. Three sets of heat pipes are used in the system. These include sodium/molybdenum heat pipes to transfer heat from the reactor core to the conversion system, potassium/niobium heat pipes to couple the conversion system to the radiator in a redundant manner, and potassium/titanium heat pipes to distribute rejected heat throughout the radiator surface. The designs of these units are discussed and fabrication methods and testing results are described.

Low-temperature heating system for buildings

Abstract: The exchanger panels (110) of the heat receiver (10) of the heating system are arranged in the side surfaces of a body stump in an air duct (120) which is controllable with a coaxial fan (160). The throughflow system, which is formed by the exchanger panels (110) and works down to at least -15 DEG C, is arranged both for direct heat transport to the heat pump (15) as required and for indirect heat transport to the long-term heat accumulator (33) as required, it being possible to make the heat for the consumers available as required from the long-term accumulator (33) or from the heat receiver (10). The heating system is especially efficient and economically favourable by virtue of the controllable capacity constancy of its heat receiver and by virtue of the stockpiling supply of the consumers.