HPC' |
HPC' |
|
G. Grazzini
|
DIRECT EVAPORATION STEAM EJECTOR REFRIGERATION PLANT |
|
G. Grazzini and A.
Rocchetti A numerical optimisation of a steam ejector refrigeration plant have been carried out, based on the Complex optimisation method. The plant is treated as an open system exchanging thermal power with three water flow rate. Ejector is a two stage with annular primary in the second stage. The heat exchangers are shell and tube with external water in the tubes. For the evaporator the solution with shell and tube is compared to that with flash chamber. Better performances are obtained for the plant with flash evaporation. In this plant configuration, a very little evaporation area and, therefore, short heat exchanger dimensions are obtained. However, the numerical flash evaporation model used requires high solving time and gives worse statistical distribution of simulation results. | |
|
Ch. Mostofizadeh
|
THEORETICAL AND EXPERIMENTAL INVESTIGATION OF A TWO-PHASE / TWO-COMPONENT EJECTOR FOR COLD PRODUCTION |
|
Ch. Mostofizadeh, D. Bohne In order to make use of low-temperature heat (solar heat, residual heat), the possibility was investigated of using a two-phase/two-component ejector which operates with ammonia/water as the working mixture. Both the primary, which is under high pressure, as well as the suction flow comprise two-phase flows with specific vapour contents. The purpose of this is to align the velocities in the mixing section in order to reduce the losses. The objective is to improve the efficiency of the ejector. The calculation of the two-phase/two-component ejector will be discussed in this paper. On the basis of the theoretical calculations, an ejector refrigeration plant with a cold capacity of 20 kW was constructed. The results will be reported in detail. | |
|
J.I. Hernández
|
PARAMETRIC STUDY OF A SINGLE REFRIGERANT COMPRESSION-ENHANCED EJECTOR REFRIGERATION SYSTEM WITH R142b |
|
J.I. Hernández1, C.A. Estrada1, R.J. Dorantes2 and
R. Best1 A parametric study of a compression-enhanced ejector refrigeration system, working with refrigerant 142b, is presented. The system energy and exergy efficiencies are considered and the ejector behaviour is represented by its efficiency. A unitary refrigeration capacity and an evaporator temperature for ice production are fixed when condenser and generator temperatures, intercooler pressure and the ejector efficiency are varied. The intercooler is considered without heat losses and the operation of the pump and compressor are assumed reversible. A low generator superheating is considered, as a result of assuming an isentropic expansion of the main ejector nozzle fluid. The ejector entrainment ratio, U, the system coefficient of performance, COPs, and exergy efficiency, e s, the intercooler mass flow ratio, U INT, the energy ratio, Er, -amount of pump and compressor work to the amount of generator heat- and the exergy flow rate change ratio, eEr, are evaluated. It is found, for a low intercooler pressure, that the system has the highest U, COPs and es for the lower condenser temperature and the higher generator temperature and ejector efficiency. As intercooler pressure increases, the effect of compression system causes the COPs to increase highly. In general terms, the tendency of the aforementioned parameters do not give a rule to define an optimisation criterion. However, considering the ratio of supplied energy, Er, the equipment and energy costs can be considered. It will help to determine a design point for an ejector refrigeration system, in which thermodynamic and economical aspects are used to define a system with efficient use of energy and adequate cost. Values of QGE, Wp and Wb for different TGE, TCO and pINT are also presented. |
Heat Powered Cycles Conference
Conservatoire national des arts et métiers, Paris
5, 6, 7 September 2001
E-mail : hpc.01@free.fr
