Evaporative heat transfer

Sindlady, heating surface area needs are not direcdy proportional to the number of effects used. For some types of evaporator, heat-transfer coefficients decline with temperature difference as effects are added the surface needed in each effect increases. On the other hand, heat-transfer coefficients increase with temperature level. In a single effect, all evaporation takes place at a temperature near that of the heat sink, whereas in a double effect half the evaporation takes place at this temperature and the other half at a higher temperature, thereby improving the mean evaporating temperature. Other factors to be considered are the BPR, which is additive in a multiple-effect evaporator and therefore reduces the net AT available for heat transfer as the number of effects is increased, and the reduced demand for steam and cooling water and hence the capital costs of these auxiUaries as the number of effects is increased. 

Lewis relationship The ratio of the convective heat-transfer coefficient to the evaporative heat-transfer coefficient. 

Fath, H. S.,andR. L. Judd, 1978, Influence of System Pressure on Microlayer Evaporation Heat Transfer, Trans. ASME, J. Heat Transfer 100 49 55. (2)... 

Herd, K. G., W. P. Goss, and J. W. Connell, 1983, Correlation of Forced Flow Evaporation Heat Transfer Coefficient in Refrigerant Systems, Paper B2, in Heat Exchangers for Two-Phase Applications, Vol. 27, National Heat Transfer Confi, Seattle, WA. (4)... 

Rohsenow, W. M., 1953, Heat Transfer with Evaporation, Heat Transfer—A Symposium Held at the University of Michigan, Summer 1952, pp. 101 150, University of Michigan Press, Ann Arbor. (4)... 

For the cycle, the total enthalpy change is zero. At the compressor, outside energy Wm is needed, and at the evaporator, heat transfer qm from the matter to be cooled is used to evaporate the refrigerant R-134a. 

The evaporative heat transfer eoefficient is obtained from kinetic theory as,... 

Lazarek, G.M., and Blake, S.H., (1982), Evaporative heat transfer, pressure drop and critical heat flux in small vertical tube with R-113, International Journal Heat and Mass Transfer 25, 7, pp 945-960. 

In this work, microscale evaporation heat transfer and capillary phenomena for ultra thin liquid film area are presented. The interface shapes of curved liquid film in rectangular minichannel and in vicinity of liquid-vapor-solid contact line are determined by a numerical solution of simplified models as derived from Navier-Stokes equations. The local heat transfer is analyzed in term of conduction through liquid layer. The data of numerical calculation of local heat transfer in rectangular channel and for rivulet evaporation are presented. The experimental techniques are described which were used to measure the local heat transfer coefficients in rectangular minichannel and thermal contact angle for rivulet evaporation. A satisfactory agreement between the theory and experiments is obtained. 

Stephan, P. (2002) Microscale Evaporative Heat Transfer Modelling and Experimental Validation, Proceedings of 12 International Heat Transfer Conference, Paper No. 08-KNL-02, Vol. Lpp-315-327. 

Kuznetsov, V.V., Safonov, S.A., Shamirzaev, A.S., Houghton, P.A. and Sunder, S.D. (1999) Two-Phase Flow Patterns and Local Evaporating Heat Transfer in a Vertical Rectangular Channel, Proc. Int. Conf. Compact Heat Exch. andEnh. Tech. Proc. Ind., Banff, Canada, pp. 311-320. 

EVAPORATIVE HEAT TRANSFER ON HORIZONTAL POROUS TUBE... 

Experimental results confirmed that propane (R290) is beneficial as a working fluid for low temperature heat pipes, thermosyphons, sorbers of chemical heat pumps, chillers of electronic components and for other evaporative heat transfer devices. The experimental data at the saturated condition Ts = 20°C (ps=8.4 bar, pr = p/pcr=0.197) are obtained in this series of experiments. 

EVAPORATION HEAT TRANSFER ON PARTIALLY FLOODED CYLINDER... 

It is possible to combine microscale and mini-seale effeets if to dispose the heat exehange eylindrical porous surface inside the tube coaxially with circular mini-gap (Figure 2, b). Experimental results (Figure 9) show, that such combination is favorable for the evaporation heat transfer. 

Porous covering with micro heat pipe phenomena stimulates the evaporative heat transfer near 8-10 times to compare with pool boiling heat transfer on the smooth horizontal tube. 

Stephan, P., (2002) Microscale Evaporation Heat Transfer Modelling and Experimental... 

Evaporative Heat Transfer on Horizontal Porous Tube 401... 

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