Showing papers on "Heat capacity rate published in 1978"

Combustion in heat exchangers

Abstract: The ranges of flow for which flames can stably be burnt in combustors based on extensive heat recirculation between products and reactants are examined in terms of the heat exchanger characteristics. This is important because, no matter how desirable it may be to burn poor fuels and mixtures of very low heat content efficiently, there are many applications for which the scheme would be attractive only for reasonably large throughputs and rates of energy release. A simple general theory based on the observed constant reaction temperature is shown to predict correctly the shape of the empirical curves for mixtures outside the flammability limits. Numerical correlations are obtained for a more detailed analysis of the very efficient double-spiral geometry. The results are compared with the theoretical maximum heat release rates per unit volume of flames in normally flammable mixtures. It is shown that mixtures containing only one fifth of the heat content at the normal limit of flammability in practice yield heat release rates comparable to the theoretical maximum for normal flames within the flammable range; the theoretical maximum for stoichiometric methane-air mixture should be attainable at little more than half the limit of flammability.

Method and system for the compact storage of heat and coolness by phase change materials

Abstract: While many materials and additives which will melt and freeze at various temperature levels for storing and releasing large amounts of heat thereby per unit volume have been disclosed, the packaging of these materials with suitable non-corrodible long-lasting heat exchange structures has been cumbersome and expensive. The present invention provides an inexpensive, high performance, non-corrodible thermal storage method and system adapted for use with heat storage materials of various compositions and adapted for use over a wide range of temperatures, including a heat exchanger which provides for phase change to occur approximately simultaneously throughout the volume of the entire storage mass and provides for the sites at which the phase change is occurring to be approximately uniformly distributed throughout the volume of the heat storage material. Problems of thermal expansion, stratification and sub-cooling are eliminated. Thermal storage methods and systems embodying the present system may advantageously be used for off-peak storage of electric refrigeration, cooling and heating as well as solar heating and other applications.

Process and apparatus utilizing common structure for combustion, gas fixation, or waste heat recovery

Abstract: An enclosure containing rotating blades for mechanical stirring of gaseous fluids may be a heat exchanger, flue gas energy recovery device, gas generator or combustion device. A high rotational stirring velocity increases the convective heat transfer rate, rendering it independent of the lower throughput velocity of primary fluid which can be controlled independently of the stirring speed. Primary fluid is isolated from a secondary fluid by a thermal transfer surface which is continuously swept by the swirling primary fluid and which may be the peripheral wall of the enclosure or a flow tube located proximate the peripheral wall. In one embodiment, swirling is achieved by radially-extending blade assemblies secured to a rotatable shaft at longitudinally spaced locations to establish discrete swirling zones in which fluid recirculates from the shaft outwardly, along the wall, and back toward the shaft. In another embodiment, the blades extend longitudinally, proximate the peripheral wall, from peripheries of horizontal discs which rotate with the shaft. In this embodiment, primary fluid follows a restricted helical path, maintaining continuous contact with the thermal transfer surface, away from the shaft. Either embodiment may be converted to a combustion system by igniting primary fluid in the presence of admitted air. In all embodiments, recirculation of primary fluid condensate, injected water or additive optimizes heat transfer via latent heat of vaporization and dropwise condensation. Blade rotary speed may be varied to commonly or independently control: combustion fuel and air flow; primary fluid flow; and stirring energy.

Fluid pumping and heating system

Abstract: The system utilizes a heat engine which provides shaft power and heat such as a conventional diesel engine in which part of the shaft power drives a pump for fluid to be heated; for example, a cryogenic liquid. The engine heat is used to heat and/or vaporize the cryogenic liquid in a heat exchanger. The heat available from the engine for transfer to the liquid to be vaporized is proportional to the power level of the engine. The heat required to heat the fluid to a desired temperature is proportional to the flow rate of the cryogenic liquid. By providing a loading on the engine which is proportional to the fluid flow rate, a sufficient amount of heat is provided to effect complete vaporization of the liquid, the amount of heat being directly proportional to the flow rate of the liquid. An engine radiator is provided to get rid of excess heat so that the heat supplied equals the heat required. The loading of the engine can be accomplished by a power absorbing hydraulic drive connected to the engine shaft with the hydraulic medium used to drive the cryogenic liquid pump, or alternatively by providing back pressure on an engine coolant pump, or by providing back pressure directly on the cryogenic fluid being pumped.

Low boiling point medium power plant

Abstract: A low boiling point medium power plant in which heated waste gas, such as furnace gas, geothermic steam, etc., is used as a heat source for heating an intermediate thermal medium by means of an indirect heat exchanger, and the intermediate thermal medium is used as a heat source for heating a turbine driving low boiling point medium by means of a direct heat exchanger. The indirect heat exchanger and the direct heat exchanger are rendered into a unitary structure and contained in a sealed housing together with a turbine, a generator and a condenser, whereby a compact overall size can be obtained in a low boiling point medium power plant.

Water heater temperature control system

Abstract: A water heater supplies hot water at a variable flow rate, depending on demand, and at a substantially constant, controlled temperature It comprises a heat exchanger formed with an inlet and an outlet whereby water can be supplied to and withdrawn from the heat exchanger in accordance with demand and means for passing a second fluid such as steam through the heat exchanger coil to heat the water A temperature gradient is thus established in the water in the direction of its flow through the heat exchanger A sense tube forms a substantially homogeneous mixture of different portions of the water, these portions being drawn from sampling points spaced apart along the temperature gradient and in relative proportions depending on the flow rate of the water through the heat exchanger The temperature of the water in the sense tube is detected, and control means responds to the sensed temperature for controlling the rate at which steam is supplied to heat the water Thus a combined set point and feed forward control is established that minimizes fluctuations in the temperature of the hot water as withdrawn for end uses by anticipating changes in BTU requirements

Method of and apparatus for the measuring of quantities of heat

Abstract: A method and apparatus for measuring an unknown quantity of heat in a measuring zone formed by a vessel of good thermal conducting properties is carried out in such a manner that the measuring zone is supplied with a known quantity of heat and the quantity of heat of the measuring zone is given off to a cold zone, that the temperature of the measuring zone is always kept equal to the temperature of the environment and at the same time the dissipation of heat is kept constant by keeping the difference between the temperature of the measuring zone and the temperature of the cold zone always the same, and that the known quantity of heat supplied to the measuring zone is measured at a point outside of the vessel when the unknown quantity of heat is absent and when it is present, the difference between the known quantity of heat in the absence of the unknown quantity of heat on the one hand and the known quantity of heat in the presence of the unknown quantity of heat on the other hand being the measurement result for the unknown quantity of heat. The vessel includes a known heat source and a cold source is provided which is connected with the vessel by way of a heat-conducting element.

Pressure controller for dual purpose steam turbine power plant

Abstract: At least one heat exchanger section including a conventional heat exchanger is disposed in a dual purpose steam turbine power plant to utilize steam extracted from the steam turbine to one section of the heat exchanger for the purposes of heating process fluid of an industrial process which is conducted through another section of the heat exchanger. The heat exchanger section disclosed herein is comprised of apparatus for controlling the pressure of the extracted turbine steam conducted through the one section of the heat exchanger by regulating the temperature of the industrial fluid supplied to the other section of the heat exchanger. More specifically, the heat exchanger section includes at least one conduit path for returning heated process fluid from an output end to an input end of the heat exchanger section to mix with the process fluid supplied at the input end. A flow control valve is disposed in the conduit path for regulating the flow of returned fluid to the input end. A pressure controller, comprising: a means for generating a signal representative of the pressure of the extracted turbine steam conducted through the heat exchanger; means for generating an error signal between a desired pressure set point signal and the pressure representative signal; and means for controlling the flow control valve as a function of the error signal to converge the error signal to substantially zero, maintains the pressure of the extracted steam conducted through the heat exchanger substantially at its desired pressure set point.

Plant for the centralised generation of thermal energy

Abstract: An installation for the central production of useful thermal energy for the remote supply of loads (10) has a turbine (16), after which one or more heat exchangers (22, 23) are connected. In these heat exchangers (22, 23), the heat transfer medium used for the remote supply is heated. In order to be able to use the mechanical energy of the turbine (16) for heating the heat transfer medium also, the turbine (16) drives a heat pump (8) which draws heat from the environment, raises it to a higher temperature level and imparts it to the heat transfer medium as useful heat. As a result, the consumption of primary energy is lower than in the case of direct heating of the heat transfer medium by primary energy alone.

Air conditioning system employing non-condensing gas with accumulator for pressurization and storage of gas

Abstract: An air conditioning system for an enclosed space employing a unitary compressor and expander of the positive displacement type, each having an inlet port and an outlet port, with a primary heat exchanger connected between the compressor outlet port and the expander inlet port and a secondary heat exchanger connected between the expander outlet port and the compressor inlet port to complete a closed loop having a charge of gas, the gas being non-condensing at the temperatures and pressures encountered in the unit. An accumulator holds an auxiliary charge of the pressurized gas at a pressure which is lower than the pressure existing in the primary heat exchanger and higher than the pressure existing in the secondary heat exchanger. A first intermittently operated valve couples the accumulator to the secondary heat exchanger for injection of auxiliary gas into the closed loop to raise the pressure in the secondary heat exchanger substantially above the atmospheric level to increase the heat rate of the system. A second intermittently operated valve couples the accumulator to the primary heat exchanger so that air is bled from the primary heat exchanger to decrease the heat rate of the system. The valves have a common operator arranged to operate the valves alternatively. It is one of the distinctive characteristics of the present invention that the loop is free of any intentional restriction in the form of a capillary or the like, or any change of phase, so that the system may be switched between high and low heat rates without risk of the "slugging" or "starvation" encountered in conventional air conditioning systems.

Heating method and bi-modal heating system for heating of buildings

Abstract: Heating system that is operated in a first mode of action, at night to low ambient temperature as an absorption heat pump, and in a second mode of action, at a low ambient temperature, as the evaporation condensation system. In the first mode of action fluid operating medium evaporates at low pressure in an evaporator (1) where it removes heat from the environment. The evaporated operating medium is absorbed by an absorbent in a vessel (2) situated absorption liquid which is pumped into a boiling vessel (8) for expelling of the working medium by heating. The operating medium is condensed at a higher pressure in a condenser (14) under release of heat to, for example, the water of a central heating system. In the second mode of action, the absorption liquid stored in the Absorptionsegefass (2) and the evaporator (1) and the absorption vessel (2) are shut off from the rest of the system. Operating medium is evaporated in the boiling vessel (8) and in the condenser (14) is condensed with release of heat.

Some considerations on the evaluation of thermal stress in combustion engine

Abstract: When power output of automobile engine increases adverse effects resulting from increase of heat load on piston become serious. For a cooling countermeasure it is necessary to clarify the path along which heat is transfered and to be familiar with heat coming from the top surface of piston. In case of small pistons without a forced cooling system at the inside face of piston, most of the heat flows out of piston toward cylinder line through the sliding surface of piston ring and piston. The research results make evident that fluttering of piston way receives heat in a reciprocating way on rear and upper surface. A set of graphs represent thermal field change in twelve moments of operating cycle. /SASI/

Heat engine and thermodynamic cycle

Abstract: Method of and apparatus primarily for converting source heat to work characterized by a gas phase working fluid thermodynamic prime mover cycle of isentropic temperature rise followed by heat acquisition followed by isentropic temperature drop followed by heat rejection to a heat sink accomplished by a variety of embodiments. Although deemphasized herein, it is further characteristic that these same embodiments going through the same motions in the same directions will to a limited extent pump heat to the heat source at the expenditure of work should the temperature difference of the sink/source become smaller than required for prime mover operation. In this invention, heat is exchanged between the compressed working fluid and the hot body only and the expanded working fluid and the cold body only.

Heat store using metal hydride, pref. magnesium hydride, as medium - has two heat transfer cycles, minimising useful heat loss

Abstract: Heat store uses metal hydrides (I) as storage substances, which release H2 on taking in heat and liberate heat on recombination of the metal with H2 and a heat transfer medium for conveying the heat to the consumers. Several stages are employed, at least one of which acts as operating stage. The operating stage and consumer or heat source are arranged in a cycle for the heat transfer medium and a second cycle is provided, by which perceptible heat is transferred from stages before the operating stage to later stages. Stores of this type are important in many technical applications, e.g. for balancing load maxima and minima of power stations, overnight storage of heat for heating purposes and storage of solar energy. The store minimises the loss of useful heat and hence of efficiency.

Closely coupled two phase heat exchanger

Abstract: A closely coupled two phase heat exchanger. The heat is transferred between gas streams by multiple intermediate fluid paths. Each of the several intermediate fluid paths passes alternately between the hot and the cold gas stream many times during its travel from the pump. The heat exchanger is designed so that the intermediate fluid vaporizes in the hot and condenses in the cold section each time, thereby minimizing the quantity of liquid necessary to transfer the heat. The pumping action for the intermediate fluid exchanger is accomplished by either mechanical or vapor pumps. An added feature of the heat exchanger is automatic control of the minimum temperature to which the hot gas is cooled. This is accomplished by shutting off one of several intermediate fluid paths at the cool end of the gas being cooled. The shutoff is accomplished either on the basis of temperature of the cooled gas or on the formation of condensates at the cool end of the gas flow path.

Liquid-fluidized-bed heat exchanger design parameters

Abstract: Liquid-fluidized-bed heat exchangers prevent scale accumulation on heat transfer surfaces and reduce the required heat transfer surface when scaling fluids, such as geothermal water, are used as the primary or working fluid. Liquid-fluidized-bed heat exchangers, principles of operation, and design parameters are described. Horizontal and vertical assemblies are discussed, including problems encountered with both designs. Bed-side heat transfer coefficients are given for limited cases, and a correlation is provided for calculating heat transfer coefficients for horizontal assemblies. A design example for a 60 kW/sub (e)/ (60 kW/sub (electric)/ preheater is included.

A General Method for the Evaluation of Possible Systems for Electric Generation with Solar Energy

Abstract: The purpose of this paper is the development of an easily applied general method of analysis of any type of potential system for electric generation with solar energy. It assumes that data for the site of the potential solar-electric plant collected over a period of ten or more years are available. The most important such data for this analysis are the mean annual insolation per unit area, I, in Btu per square foot (Btu/ft2), and the peak rate of solar insolation, P, in Btu/ft2 hr. Secondary site data include the mean number of hours of sunshine on the site per year, measures of the seasonal variation between summer and winter, and the frequency of damaging storms. For the proposed solar-electric generating plant, only two characteristics are required: the gross heat rate, H, in Btu of solar radiation received on the collectors per kilowatt hour (kWhr) of electricity delivered in usable form, and the amount and efficiency of energy storage included in the plant. The heat rate for the system depends on a series of efficiencies or losses as the received solar radiation passes through successive stages of the system to its electrical output. For fully engineered systems it can be estimated within fairly narrow limits. For k speculative systems which might materialize as a result of future research and development, an assumed value can be chosen on the basis of what is hoped to be achieved.

Method for converting heat energy to mechanical energy with monochlorotetrafluoroethane

Abstract: Monochlorotetrafluoroethane is useful as a power fluid with particular suitability for large scale Rankine cycle applications based on systems with moderate temperature heat sources. The fluid is utilized in a Rankine cycle application by vaporizing the fluid by passing the same in heat exchange relationship with a heat source and utilizing the kinetic energy of the resulting expanding vapors to perform work. In this manner heat energy is converted to mechanical energy.

Investigation of methods to transfer heat from solar liquid-heating collectors to heat storage tanks. Final report

Abstract: A study was made of the methods available to transfer heat from the collector to the water storage tank in water heating systems. In counterflow heat exchangers used in double loop water heating systems, it was found to be more important to use a high water flowrate than a high heat transfer fluid flowrate. It was earlier thought to be best to have matched WC/sub p/ (mass flowrate-specific heat) products in the loops. It was shown in this study that the water WC/sub p/ product should be about twice as large as that of the heat transfer fluid. It was found that neither the heat exchanger type nor the size was very critical, so that very simple criteria were adequate in determining optimum heat exchanger size. It was found that there is a definite system size below which one should use a traced tank or a coil in a tank. Equations and optimization criteria were developed for traced tanks or tanks with coils. At present, there is no quantitative understanding of liquid to liquid (direct contact) heat exchangers, though they are clearly quite effective. Draindown systems are discussed, and several appendices are included on heat transfer and other characteristics ofmore » fluid and of equipment.« less

Optimizing a heat pump for heating purposes

Abstract: A computer simulation routine is used to analyse the economic effects of varying the heat exchangers and fans of a 3 hp commercial (base-line) air-air heat pump, on the assumption that it is used only for heating purposes. Both long-term (life-cycle costing) and short-term (pay-back time) economic measures are considered. the results indicate that there is economic justification for substantial increases in the capacity of the heat exchangers of the base-line unit. Such an optimized heating-only heat pump has technical and energetic advantages over the base-line unit.

Solar heat collection and transfer system

Abstract: A fluid system for controlling fluid temperatures and transferring heat from a solar energy collector to a point-of-need heat exchanger, remote from the collector, from which heat is discharged for use. Heat is collected by the fluid in the solar collector, which fluid flows by natural circulation into an accumulator, connected in a continuous heat accumulation loop with the collector. A self-energized forced-convection heat transfer loop leads from the accumulator to the lower discharge heat exchanger and back to the solar collector. The fluid system blanket pressure, i.e. the pressure at the high point of the system, is maintained at a level such that the fluid vaporizes in the temperature range of the solar collector. Vapor energy is extracted from the blanket vapor in the accumulator to energize an injector pump in the forced-convection heat transfer loop to motivate the heated fluid through the loop from the accumulator to the point-of-need heat exchanger for practical use.

Operation controlling method of power plant

Abstract: PURPOSE: To control the operation of a safety power plant, by means of controlling the solubility of a medium in the exchanger at a constant by regulating the flow quantity to the direct type heat exchanger of the power plant. CONSTITUTION: The heat of a fluid 1 of a heat source is conducted to a high temp. heat medium 3 by a heater 2, and is led to a direct type heat exchanger 4 along with a low b.p. medium used by a turbin. a pressure P of the heat exchanger 4 is detected, and a set temp.T is determined by detected value thereof. The temp. of the high temp. heat medium 3 is detected by a detector 16, and is added by means of introducing to a low b.p. medium flow quantity control device 17 along with a signal of the set temp.T. In a case when the result is negative, it shows that the portion of the temp. of the high temp. heat medium is lower, and the temp. is raised by means of reducing th flow quantity of the low b.p. medium by choking a flow quantity control valve 11 for the purpose of raising the temp., and of reducing the evaporated quantity in the inner part of the heat exchange 4. In a case when the heating value is positive, the reversed control said above is effected. COPYRIGHT: (C)1979,JPO&Japio

Closed heat transfer system

Abstract: A closed heat transfer system which is capable of providing more efficient heat transfer by virtue of the fact that a small fuel burner is operated for a longer period of time but with much less consumption of fuel than compared to a conventional cycled heating system. The system includes a heat sink containing a suitable heat storage fluid, a heat source, heat transfer means, a preheater means, hot water feed means, and circulator means. The heat sink preferably takes the form of a closed container operable in the manner of a boiler and filled with a suitable heat storage fluid.

Heat transfer characteristics of a gas-to-gas heat exchanger using heat pipes

Abstract: The heat transfer characteristics of a gas-to-gas heat exchanger employing heat pipes as the heat transfer elements were examined. Experimental data obtained on the heat exchanger containing 66 finned heat pipes were compared with the values calculated by using various empirical and theoretical equations. A basic design procedure for gas-to-gas heat exchangers using heat pipes was then established. The results showed that: for the overall heat transfer coefficient, the measured values were in fair agreement with the values calculated using the empirical and theoretical equations; for the outside heat transfer film coefficient including the fins' thermal resistances, the measured values were in good agreement with the calculated values if a suitable compensation is made for the latter with respect to the average gas bulk temperature; vertical positioning of heat pipes is more advantageous than horizontal positioning; the difference in heat transfer performance between them becomes greater with the increase of heat flow through the heat pipes; and measurements of the pressure drop across the heat pipe bank show somewhat lower values than those calculated, but the equation used for calculation is considered feasible as a design formula.

Closed loop air conditioning system including pressurization by blockage and aspiration

Abstract: An air conditioning system for an enclosed space including a jointly driven compressor and expander of the positive displacement type each having an inlet port and an outlet port with a primary heat exchanger connected between the compressor outlet port and expander inlet port and a secondary heat exchanger connected between the expander outlet port and the compressor inlet port to complete a closed loop having a charge of air and with one of the heat exchangers being thermally coupled to the enclosed space. Ambient air is injected into the closed loop to raise the pressure in the secondary heat exchanger to substantially above the atmospheric level to increase the heat rate of the system. Alternatively air is bled from the loop to reduce the pressure in the secondary heat exchanger thereby to decrease the heat rate of the system. In one embodiment of the invention a blocking valve in the path of the air stream flowing through the secondary heat exchanger is momentarily closed to create a vacuum at the compressor inlet port and an injector valve at the compressor inlet port is coincidentally opened so that ambient air is injected by the process of aspiration. While the system may be manually controlled, it is one of the features of the invention that injection and bleeding are under the automatic and corrective control of a temperature pressure sensing device so that the heat rate of the system is varied automatically in accordance with the requirements of an enclosed space for automatic maintenance of a present condition. The system is usable in a refrigerating mode, making use of the absorption of heat in the secondary heat exchanger or in the heat pump mode utilizing the dissipation of heat in the primary heat exchanger, with automatic control of space temperature in both of the modes.

Method for converting heat energy to mechanical energy with 1,2-dichloro-1,1-difluoroethane

Abstract: 1,2-Dichloro-1,1-difluoroethane is useful as a power fluid with particular suitability for moderate scale Rankine cycle applications based on systems with moderate temperature heat sources. The fluid is utilized in a Rankine cycle application by vaporizing the fluid by passing the same in heat exchange relationship with a heat source and utilizing the kinetic energy of the resulting expanding vapors to perform work. In this manner heat energy is converted to mechanical energy. The fluid is particularly advantageous in a dual cycle system consisting of a Rankine power cycle combined with a vapor compression cooling or heating cycle. BACKGROUND OF THE INVENTION

Exact and approximate solution of the regenerator equation for the case of high heat exchange and moderate heat capacity

Abstract: If the inflow temperatures are constant the regenerator equation can be transformed into an integral equation. The latter is solved numerically by an iteration procedure. From the results, a simple approximate solution is found for the case of high heat exchange (30<Λ<300) and moderate heat capacity (1.5<Γ<3).

Control of waste heat recovery from highly heated substance

Abstract: PURPOSE: To control conditions for cooling in a high temperature region where preset heat quantity is reached by measuring the sensile heat of a highly heated substance to be charged into a cooler in the heat exchanger for waste air, in which system high temperature system is separated from low temperature system, and then by calculating the heat quantity of waste air after cooling in the high temperature region. CONSTITUTION: In the cooler 1 for sintered ore, for example, in which the high temperature region 1A is separated from the low temperature region 1B, the forced circulating system for cool air is divided into the systems 2A and 2B, and the heat quantity of waste air necessary as steam-generating source is beforehand set up and then memorized in the flow rate setting device 12. The actual heat quantity of waste air in the high temperature region is calculated by the sensible heat operator 11 from the values measured by the radiation pyrometer 9 and the heat ray anemometer 10, and then the value obtained is compared with the aforesaid set value. If there is a difference between them, the conditions for cooling of high heated substance in the high temperature region is regulated to control the temperature of waste air after cooling so as to keep it constant. Thus, even if the operational conditions are varied, it is possible to obtain constantly steam, etc., all the time. COPYRIGHT: (C)1979,JPO&Japio