摘要:

AbstractThe paper presents exact analytical solutions of one‐dimensional periodic heat conduction through an inhomogeneous slab for a certain class of thermal conductivity profiles (including linear and exponential). The exact analytical solutions for some of these profiles have been compared with those obtained by considering the slab to be made up of a number of homogeneous layers with different thermal conductivities varying from layer to layer and using the layered structure (or matrix multiplication) method. The numerical results arrived at by the layered‐structure method converge rapidly (with increasing number of layers considered) to the values obtained from the exact analytical solutions. This gives confidence in the application of the layered‐structure method to periodic heat conduction through inhomogeneous slabs. The numerical results have been presented in the form of elements of a 2 × 2 matrix, relating the sinusoidal steady‐state temperature and heat flux on the two sides of

ISSN:0363-907X    

DOI:10.1002/er.4440160902

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn the paper, conditions for multi‐unit heat pump (MUHP) stationary operation at the level of condenser and evaporator groups and in a system are considered. The matrices describing the equilibrium operation are defined, and the methods of their determination are describe

ISSN:0363-907X    

DOI:10.1002/er.4440160903

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn the paper, a method for the determination of the parameters of the units, stationary operating in a multi‐unit heat pump system, is presented. This method is used for the consideration of six schemes of hydraulic connection of the heat exchangers in group

ISSN:0363-907X    

DOI:10.1002/er.4440160904

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA simple and inexpensive electrical circuit based on the transient probe method has been developed for the determination of thermal conductivities of building and insulating materials namely limebrick, gypsum, rockwool and polystrene foam. The solution of the unsteady state heat conduction equation has been approximated by considering certain simplifying assumptions which have been justified by experimental observations. The overall accuracy of the thermal conductivity measurements is estimated to be within ± 3%

ISSN:0363-907X    

DOI:10.1002/er.4440160905

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper presents an optical design based on a single‐reflection criterion, and performance characteristics of an east‐west aligned nontracking seasonally adjusted linear trough solar concentrator with a flat horizontal absorber, using plane mirror elements. The design procedure allows the use of any desired number of mirror elements to reflect solar energy onto the base absorber in one reflection. The angle of inclination of each mirror element with respect to the absorber surface, and the width of the mirror element, are determined so that a ray incident on the extreme upper edge of the mirror element at a specified angle to the normal to the concentrator aperture (acceptance half‐angle), after reflection, strikes the extreme edge of the absorber on the opposite side of the mirror element. Other rays making angles less than the design acceptance half‐angle are also reflected onto the base absorber in one reflection. Concentrator designs resulting from this approach appear to have the important characteristic of relatively smaller heights, and hence appear highly cost‐effective in terms of the amount of material required for fabrication. Some numerical calculations have been carried out to illustrate the performance of concentrators for different acceptance half‐angles. Results obtained are presented in graphic and tabular forms, and ar

ISSN:0363-907X    

DOI:10.1002/er.4440160906

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA high‐temperature chemical heat pump based on the system acetone/H2/2‐propanol for waste heat recovery was studied. Two reversible catalytic chemical reactions are involved in this system. The waste heat (at 333–353 K) is recovered by means of the endothermic liquid‐phase dehydrogenation of 2‐propanol, and is upgraded at high temperature (453–473 K) by the reverse reaction, the exothermic gaseous‐phase hydrogenation of acetone. In this process, a fraction of the recovered waste heat is removed at low temperature (303 K), to carry out the separation by vapour rectification between acetone and 2‐propanol.A mathematical model was developed, that permits the study of the effect of the heat pump operating conditions on the energetic performance (COP), exergetic efficiency and size parameters. Also, this model allows the estimation the optimal range for the system control variables. Under these conditions, the energy and size parameters have been calculated on a basis of 0.32 M

ISSN:0363-907X    

DOI:10.1002/er.4440160907

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper presents an analysis of the cycle‐by‐cycle combustion variation as reflected in the pressure indicator diagram of a single‐cylinder, naturally aspirated, four‐stroke, direct‐injection, Lister LV1 diesel engine. A measuring set‐up consisting of piezoelectric transducers with charge amplifiers, in the cylinder and the fuel injection pipeline, and a fast data‐acquisition board installed on an IBM‐compatible microcomputer was used to gather the data of 650 successive combustion cycles of the cylinder, under various combinations of injection timing and load conditions. The measured data were corrected for drift, and the top dead centre of each cycle is determined thermodynamically. The data obtained by this technique were analysed for the peak pressure, the peak rate of pressure rise, the crank angles at which these maximum values occur, and for the injection timing and ignition delay. The groups of parameters have been further statistically analysed for averages, standard deviations, probability density functions, autocorrelations and power spectra. Crosscorrelation runs were also performed to observe any cause relationship between cyclic pressure variations and the fuel‐injection‐system operation. The results of the stochastic analysis technique have proved to be very useful for the investigation and interpretation of the existence of fluctuation phenomena in the diesel internal combustion engine and their cause relationships, thereby aiding the correct interpretation of the relevant experimental results and thei

ISSN:0363-907X    

DOI:10.1002/er.4440160908

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe thermal and fluid mechanical properties of an evaporative capillary pump are described by means of characteristics that have been determined by tests. The capillary pump, which has been newly designed for an application in future space projects, serves a double function as the heat absorbing element in a closed loop as well as a pump circulating the working fluid. The working fluids used were CCI3F (freon R11) and liquid anhydrous ammonia. The paper describes the associated heat and mass transport in the capillary pump, and the physical process of the capillary pumping is explained. Furthermore, a model is introduced which explains the boiling heat transfer in the porous structure of the capillary pump.

ISSN:0363-907X    

DOI:10.1002/er.4440160909

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA chemical heat pump, based on the reversible reaction couple of thei‐propanol‐acetone system, was investigated experimentally. The endothermic dehydrogenation ofi‐propanol occurred at 80°C with a Raney nickel catalyst suspended in the liquid phase. The unreactedi‐propanol was separated from gaseous products in a condenser. The exothermic hydrogenation reaction of the acetone was performed at 200°C and 1atm, in the presence of the Raney nickel catalyst. The positive value (ΔG) of the change of Gibbs free energy can make the dehydrogenation reaction ofi‐propanol rather difficult. This problem can, though, be overcome by the continuous removal of gaseous acetone and hydrogen products from the reaction medium. The dehydrogenation rate equation ofi‐propanol was obtained asV= 0.1 Cp/(1 + 7.0 CA). The gas phase hydrogenation reaction of acetone was performed in an exothermic tubular reactor. In order to estimate energy efficiency, a simulation of the separation stage was performed. Based on these experimental and simulation results, the optimal design specifications for the chemical heat pump were determined. The maximum hydrogenation of acetone was obtained when the mole ratio of acetone to hydrogen was 4.0. Energy efficiency was increased when the conversions of hydrogenation and dehydrogena

ISSN:0363-907X    

DOI:10.1002/er.4440160910

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe traditional approach to energy planning has been to determine the energy demand and then to plan the supply accordingly. However, the current situation calls for a methodical approach where environmental degradation, economic growth and technological efficiency are to be considered. Modified and mathematical programming energy economy environment models have been built to meet these requirements for India. The gap between the requirements predicted by the modified model and the optimum requirement from the MPEEE model must be supplied by nonconventional sources. A Delphi study was conducted to determine the possible percentage utilization of nonconventional sources, keeping in view technology, emission, availability and social acceptance. Statistical tests of consensus and stability gave positive results. The reasons for using and not using the various nonconventional energy sources were determined along with their priority of usage in different sectors. The Delphi study helped in arriving at a quantitative decision with regard to social acceptance and percentage allocation of the nonconventional energy sources.

ISSN:0363-907X    

DOI:10.1002/er.4440160911

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY