Showing papers on "Thermal efficiency published in 1986"

Solar-powered rankine cycle pumping engine

Abstract: The invention is a solar-powered, Rankine cycle, two fluid, engine useable for many functions, especially for pumping liquids from the ground such as water or oil in remote locations. The engine driven by heat energy collected in standard collectors or in solar ponds utilizes a heated fluid such as water to transfer the heat from the collectors to a tank where a volatile working medium is transformed into a pressurized vapor. The heated working medium is then fed to a double acting cylinder where work is extracted from the working medium. The engine is a rather slow moving engine, with the valving controlled by electric switches which are driven by storage batteries. The storage batteries are continuously charged by solar energy. If the source of energy is heat collected by standard collectors, a tracking device for the collectors, also driven by solar power, is incorporated in order to attain high collection efficiencies. The engine is used to drive either mechanical or hydraulic pumping devices. The invention is especially suited to remote locations, and for those purposes where constant vigil of the engine is impractical. The engine and the accessories are self sufficient in that they require little or no maintenance, and are not dependent on a fuel or electricity supply.

Latent Thermal Storage Unit Using Form-Stable High Density Polyethylene; Part I: Performance of the Storage Unit

Abstract: A latent thermal storage unit of 30 kWh using form-stable high density polyethylene (HDPE) rods has been developed mainly for solar thermal applications, and heat transfer experiments have been carried out. A direct contact heat transfer technique between HDPE rods and ethylene glycol (EG: a heat transfer fluid) is adopted. Charge and discharge characteristics have been obtained for various thermal input/output and different initial temperature profiles in the storage unit. The direct contact heat transfer and a formation of a clear thermocline provide a good performance for all the cases. Discussions are given of thermal efficiency, storage density, and thermal insulation.

Radiant tube heating system

Abstract: A gas-fired radiant tube that employs heterogeneous catalytic combustion, and a high combustion efficiency, low NOx catalytic combustion radiant tube heating system, incorporating the radiant tube, are disclosed. In the system, essentially mirror image, combined inlet/exhaust units containing heat regenerator units are connected at opposite ends of the catalytic combustion tube. Combustion flow is cycled back and forth through the units and the combustion tube so that during any given cycle the hot exhaust gases heat the regenerator in the exhaust side of the flow for preheating the inlet gases during the next, reversed flow cycle and the natural gas fuel is completely oxidized. Thus, the cycled flow completely consumes the fuel and constantly preheats inlet air so that the sytem provides both high combustion efficiency and high thermal efficiency.

Turbo compound internal combustion engine

Abstract: A turbo compound internal combustion engine (1) has an electrical generator (6) driven by an exhaust turbine (5) for converting the exhaust gas energy of the engine (1) to electric energy and an electric motor (12) operatively coupled to the output shaft (1d) of the engine. The motor (12) is driven by the electric energy generated by the generator (6) so that the energy of the exhaust gas can be recovered. The torque produced by the engine (1) is assisted by the motor (12) in dependence on the speed of rotation of the output shaft (1d) of the engine.

Solid electrolyte fuel cell module

Abstract: PURPOSE:To reduce the space for adiabatic materials extensively and to improve the thermal efficiency, by furnishing air preheaters to heat the air for reaction from a reaction air inlet, which are installed in a module shell, a reaction chamber to which the heated air is fed, a combustion chamber, and a solid electrolyte fuel cell main body installed at the reaction chamber and the combustion chamber. CONSTITUTION:The air for reaction is led from a reaction air inlet 12 to the inside of a module shell 11 at a normal temperature, and introduced to a low temperature air preheater 14 through a reaction air header 23. The air heated at the low temperature air preheater 14 is heated further at a high temperature air preheater 15, and led to a reaction chamber 17 through a reaction air pouring pipe 24. On the other hand, a reaction hydrogen is led to a solid electrolyte fuel cell (SOFC) main body 21 from the inlets 22a of introduction pipes 22, the hydrogen which is not utilized in the SOFC main body 21 is made into a burned gas in the combustion chamber 18, fed to the high temperature air preheater 15, and, after the heat is recovered there, exhausted to the outside from an exhaust gas outlet 13. In such a way, as well as the space for adiabatic materials is reduced extensively, the thermal efficiency can be improved.

Heat Transfer in Oil-Flooded Screw Compressors

Abstract: Thermodynamic efficiency of the compression process in oil-flooded screw compressors depends greatly on the oil-gas heat transfer process. The amount of heat transfer is a function of many parameters such as mode of oil injection, oil inlet temperature, etc. This paper describes a mathematical model to calculate this heat transfer, assuming that the oil is injected in the form of non-interacting spherical droplets. The droplet trajectories are calculated from the point of injection to the point where the droplets hit the moving boundaries of the compressor rotor. The overall heat transfer is calculated by summing the heat exchange over all the droplets during their free-flight time. This model is then used to calculate the effect of such heat transfer on compressor performance. Some guidelines on ways to enhance heat tran~fer are also provided.

Minimum Energy Control of a Large Diesel Engine

Abstract: The thermal efficiency of a large ship diesel engine is determined mainly by the design of the engine/propellor combination but small efficiency increments can be obtained through the careful design of automatic controllers for the system. A fuel saving regulator requires an accurate model for the internal states of the engine in order that its thermal efficiency can be maximized. Such a model has been recently obtained by one of the authors. This model has been shown to give accurate estimates of the thermal efficiency which can be expected under normal sea conditions. Using the model as a basis an adaptive energy minimizing controller has been designed and tested. Depending upon sea conditions, simulations suggest that fuel savings on the order of 0.5% can be expected. Though small percent-wise savings on this order could more than pay for the installation costs of the regulator during the first year of use. The project is carried out in cooperation with M.A.N.-Burmeister and Wain Diesel A/S, Copenhagen Denmark.

Heat-exchanger for fuel in an internal combustion engine

Abstract: An heat exchange arrangement for a fuel system of an internal-combustion engine vehicle utilizing a heat pipe with an evaporizing zone for cooling the fuel directed from the engine to the fuel tank and a condensation zone located in an air path of the vehicle

Design study for a low heat loss version of the Dover engine

Abstract: The paper describes an analytical and hardware design study aimed at evolving a low heat loss version of a current turbocharged production diesel engine, the Ford Dover engine.The analytical approach was done using the Ford engine simulation program and aimed to establish whether reduction in heat loss would be advantageous for this particular engine. Various levels of insulation were assumed on the piston crown, the cylinder head and the cylinder liner, and the effect on power output and fuel economy was assessed. It was found that reduced heat loss could be implemented without any major design changes and would result in benefits in both power output and fuel economy. New pistons and alterations to the combustion space were then evolved and specified in detail to bring about the desired reduction in heat loss. Thermal analysis of these designs using finite element and other approaches confirmed their suitability.The paper describes the approach, the various stages in the development of the designs, thei...

Pulse combustion engine and heat transfer system

Abstract: A pulse combustion powered apparatus is disclosed for temperature conditioning and pressurizing fluids The alternating periods of positive and negative pressure of the combustion gases of a pulse combustion burner drive a reciprocating compressor and the rejected engine heat is recovered by heat exchange with a primary fluid The compressor may be included in a reversible refrigeration circuit to provide heating and cooling of secondary fluids

Closed cycle external combustion engine

Abstract: An external combustion engine which utilizes an impulse or velocity compounded turbine in conjunction with a compressor to reduce input energy requirements while delivering an increased work output. The invention is characterized in the use, simultaneously, of cooling and compression, significantly to reduce the compression work requirement of current practices (which utilize interstage cooling between compression cycles). In accordance with the present invention the fluid is cooled in the compressor itself, during the compression cycle, and heat energy losses inherent in conventional cycles are reduced. The efficiency of the engine is increased significantly. An important feature of the invention is that phase change or transformation is eliminated, so that heat energy is conserved. In a second embodiment of the invention, the engine utilizes one or more impulse or velocity compounded turbines, and expansion is limited to a range in which compression is carried out with a minimization of parasitic losses. Any work sacrifice attributable to low pressure output portions of the cyclical operation is compensated for by a substantial salvage of the heat ordinarily dissipated and lost as waste in conventional cycles.

Magnetic Refrigeration Study at CEA Grenoble

Abstract: Two kinds of applications are considered for magnetic refrigeration, first in the 18 K range mainly for He II cooling of superconductors and second for He I refrigeration with precooling near 20 K At He II temperatures, refrigeration by a Carnot cycle has been investigated and analysed We give a survey of the results which demonstrate the capability of magnetic refrigeration to attain high thermodynamic efficiency More interest is now devoted to He I cooling for which we compare magnetic refrigeration to the standard existing solutions For temperatures higher than 10 K, we discuss the interest and the constraints of cycles with internal heat exchange Analysis of various configurations is given to explain the choice of a new experiment being built

On the thermodynamic efficiency of solar energy converters: Solar cells

Abstract: Assuming that both source and energy converters are blackbodies and applying thermodynamic balance equations, the net efficiency of a solar cell is derived as a product of two different efficiencies associated, respectively, with the energy absorption and energy conversion into useful work. At room temperature the maximum net efficiency thus obtained is 38%. Efficiencies are calculated at various solar cell temperatures, and results are discussed in view of existing theories.

Improvement of liquefaction efficiency of the heat pipe type magnetic refrigerator

Abstract: The Carnot type magnetic refrigeration in the temperature range from 4.2 K to 15 K has been studied. This paper describes the additional experimental results to improve the liquefaction efficiency. The liquefaction losses in the demagnetization process largely depend on the gap width of the heat pipe-GGG system. At each initial temperature, there was an optimum gap width and magnetic field sweep rate. The maximum liquefaction efficiency was obtained for the gap width of 400 to 600 µm at 4.2 K.

Reboiler system for glycol dehydration having improved thermal efficiency

Abstract: A reboiler for dehydrating glycol used in a gas dehydration system having improved thermal efficiency including a horizontal boiler vessel, a horizontal heater within the boiler vessel having a fuel burner therein, a heat exchange vessel extending downwardly from the boiler vessel including piping to receive heated glycol therein from the interior of the boiler vessel and a heat exchange conduit within the heat exchange vessel extending exteriorly of it, one end of the heat exchange conduit communicating with the interior of the boiler vessel to transfer wet glycol into the boiler vessel and a glycol inlet at one end of the conduit extending externally of the vessel and the heat exchange vessel having a dehydrated glycol outlet, hot dehydrated glycol from the boiler vessel passing downwardly through the heat exchange vessel to thoroughly exchange heat with the incoming wet glycol to thereby conserve heat applied to the glycol for dehydration.

Steam Injected Gas Turbine Integrated With a Self-Production Demineralized Water Thermal Plant

Abstract: A simple steam injected gas turbine cycle equipped with an exhaust heat recovery section is analyzed. The heat recovery section consists of a waste heat boiler which produces the steam to be injected into the combustion chamber and a self-production demineralized water plant based on a distillation process. This plant supplies the pure water needed in the mixed steam-gas cycle.Desalination plant requirements are investigated and heat consumption for producing distilled water is given.Overall steam-gas turbine cycle performance and feasibility of desalting plants are investigated in a firing temperature range from 1000.°C to 1400.°C for various compressor pressure and steam-to-air injection ratios. An example is reported.Copyright © 1986 by ASME

A Study on the Reformed-Methanol Engine

Abstract: Selection of the optimum catalyst for the reformation of methanol, and static/dynamic characteristics of a spark ignition engine fueled with both gasoline and methanol reformed gas were studied. Tube test results on reforming characteristics show that a catalyst made of a base metal works best. A methanol reformer with an exhaust gas heat exchanger was used. Results show that the increase of reformed gas ratio increases the stability of combustion and extends the lean limit. It also improves thermal efficiency, owing to the reduced duration of combustion. Moreover, responses of Pmax during sudden opening/closing of the throttle valve were studied. Results indicate that the higher the reformed gas ratio, the quicker the Pmax response and the smoother the combustion process.

Continuous annealing method for steel strip and annealing furnace therefor

Abstract: PURPOSE: To improve the thermal efficiency of a furnace by preheating new atmospheric gas by sensible heat held in the atmospheric gas circulating in and out of the furnace at the time of executing continuous annealing, while sending new atmospheric gas into the furnace to utilize effectively the above sensible heat. CONSTITUTION: Steel strip 1 is carried in the annealing furnace 2, that is, it is heated at the heating zone 5 through inlet side sealed part 13 and inlet chute part 3 and cooled at the cooling zone 6 and is discharged to out of the furnace from outlet side sealed part 14. In this case, the new atmospheric gas is sent into the furnace 2 from gas sending hole 12 through supplying device 8 and dryer 9. Then, the atmospheric gas in the cooling zone 6 is taken out from sucking hole 18 by a circulating fan 15 to again send in from a gas sending hole 19. And by a heat exchanger 16, new atmospheric gas sent from the supplying device 8 is preheated by the sensible heat of the atmospheric gas sent from the fan 15. COPYRIGHT: (C)1987,JPO&Japio

Heat insulating gasket and manufacture thereof

Abstract: PURPOSE:To prevent heat from being dissipated from a combustion chamber to the outside, by a method wherein a gasket, formed by a low thermal conductive material having low thermal conductivity, is located between a ceramic heat insulating wall and a metallic structure. CONSTITUTION:A ceramic heat insulating wall 7 is coupled with a metallic structure 2 by means of a bolt 3 with a heat insulating gasket 4 therebetween. The heat insulating gasket 4 is formed such that a heat resistant sheet, such as stainless, cordierite, zirconia, or a metallic sheet, such as Incoroy, Kovar, having low thermal expansivity and resistance to heat, form a core 12, and a low thermal conductive material, such as potasium titanate, is attached to at least the one surface of the core. This enables heat to remarkably be prevented from conduction from a ceramics heat insulating wall 7 to the metallic structure 2, and improves thermal efficiency of a heat engine.

Exhaust silencer of heat exchanger utilizing engine

Abstract: PURPOSE:To promote the reduction of exhaust noise and the improvement of thermal efficiency, by providing an exhaust silencer, serving also as a heat exchanger, connecting with an exhaust passage arranged below a level of fluid, in the case of a device arranging an engine in a fluid tank storing the fluid for a thermal medium. CONSTITUTION:When the invention is applied to an air conditioning outdoor heat exchanger device, the device, providing an engine 14 so as to vertically arrange its crankshaft 16 in a fluid tank 12 accumulating water 10, horizontally juxtaposes a cylinder block 19a and a cylinder head 19b for a crankcase 18 of the engine. The device, providing a pipe type exhaust heat exchanger 20 in the bottom of the cylinder head 19b, connects an exhaust pipe 21a, extended from the cylinder head 19b to the bottom, with the heat exchanger 20. While the device provides in the bottom of the crankcase 18 a primary exhaust silencer 22, serving also as a heat exchanger, to be connected with the heat exchanger 20 through a communication pipe 21b. Drain water in this silencer 22 is inducted to a drain muffler 30 through a discharge pipe.

Thermally regenerative hydrogen/oxygen fuel cell power cycles

Abstract: Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

Method and apparatus for maximizing internal combustion engine work output by controlled heat release

Abstract: A method and apparatus are disclosed for controlling the rate and timing of heat released during each combustion cycle of an internal combustion engine so as to maximize the net work output of the engine. Mathematical expressions of engine loss factors, such as friction and heat transfer, are used to establish a combustion chamber pressure versus crank angle function which is analyzed together with a combustion chamber pressure versus crank angle function in the absence of combustion. From this analysis, a derivation of optimized combustion chamber heat release rate and timing is enabled. The optimized combustion chamber heat release rate and timing are achieved by controlling the timing and rate of injection of fuel into the combustion chamber, which fuel has been activated by pretreatment so to enable "hypergolic" or instantaneous combustion upon injection.

Cycle Simulations of a Coal-Fueled, Reciprocating, Internal- Combustion Engine: the Role of Volatiles and Liquid Carriers

Abstract: An engine cycle simulation was developed to investigate the role of volatiles and liquid carriers on the combustion process and performance of a coal-fueled, reciprocating engine operating at 1000 rpm. Models for coal particle combustion and devolatilization, liquid droplet vaporization, fuel vapor combustion, cylinder heat transfer, piston work, and mass flow rates were combined with a thermodynamic analysis of the engine to yield instantaneous cylinder conditions and overall indicated engine performance. Four representative devolatilization rate expressions for bituminous coal were selecled from the literature for comparison in this study. With rapid devulatilization of the coal, no external energy source was necessary to ignite and completely combust the fuel for an initial (at BDC) gas temperature of 450 K. In contrast. for no volatile evolution, an initial gas temperature of 600 K was needed to achieve maximum engine performance. The initial gas temperature was identified as a significant pa...

Small scale rice hull gas producer-gasoline engine performance

Abstract: In this study, a unique rice hull gas producer fueled a 3.7 kW, single cylinder, gasoline engine. At 3600 RPM and WOT, the engine developed 43% of the rated power on gasoline. Brake thermal efficiency was 16.8%. System thermal efficiency was 9.4%. Optimal spark advance for producer gas was 23/sup 0/.

Example of Second-Law Efficiency of Solar-Thermal Cavity Receivers

Abstract: Properly quantified performance of a solar-thermal cavity receiver must not only account for the energy gains and losses as dictated by the First Law of thermodynamics, but it must also account for the quality of the energy. Energy quality can only be determined from the Second Law. In this paper, an equation developed for the Second-Law efficiency of a cavity receiver is presented as an evolution from the definition of available energy or availability (occasionally called exergy). The variables required are all either known or readily determined. The importance of considering the Second-Law is emphasized by a comparison of the First- and Second-Law efficiencies around an example of data collected from two receivers that were designed for different purposes, where the attempt was made to demonstrate that a Second-Law approach to quantifying the performance of a solar-thermal cavity receiver lends more complete insight than does the conventional solely applied First-Law approach.

Turbostar: an ICF reactor using both direct and thermal power conversion

Abstract: Combining direct and thermal power conversion results in a 52% gross plant efficiency with DT fuel and 68% with advanced DD fuel We maximize the fraction of fusion-yield energy converted to kineti