Joanna Wilk

Forced convection mass/heat transfer coefficient at the surface of the rotor of the sucking and forcing regenerative exchanger

Abstract Experimental investigations of mean mass/heat transfer coefficients at the surface of two different curved short ducts of rotors of the sucking and forcing regenerative heat exchanger were made for forced laminar flow in static conditions. An electrolytic technique was employed. The results for two types of ducts are presented finally by correlations for jM Chilton-Colburn coefficient vs Reynolds number. The results for one of the ducts are consistent with the previous results of the author for the inner surface and developed flow in a straight annular duct with similar L/Dh.

Mass/heat transfer coefficient in the radially rotating circular channels of the rotor of the high-speed heat regenerator

Abstract Laminar forced convection heat transfer in radially rotating circular channels of the rotor of the high-speed heat regenerator has been investigated. Mean values of the convective mass/heat transfer coefficient in these channels were measured electrolytically. The measurements were made for Ro=0.1 and Ro=0, in the range of Reynolds number from 250 to 1200. The value of Rossby number and the range of Reynolds number result from the hydraulic characteristics of the regenerator. Finally, the correlations have been formulated for Chilton–Colburn coefficient vs. Reynolds number and for Nusselt number vs. Reynolds number. In order to estimate the error of the heat transfer coefficient resulting from application of the mass/heat transfer analogy, a comparison of experimental thermal investigation, mass transfer experiments using electrolytic technique and theoretical analysis results has been performed in some defined cases.

Effect of positioning the axis of a lamellar rotor model of a sucking and forcing regenerative exchanger on the intensity of convective mass/heat transfer

Abstract Mean values of the convective mass/heat transfer coefficients for two porous structures—differing in bc th profile and the value of Dh—of the rotor of a heat regenerator were measured for horizontal and vertical positions of the axis. The flow in short curved ducts of the immovable model was forced by the pump. The results of electrolytic measurements were independent of the positioning of the axis. Final correlations of the jM-factor or Sh vs Re are almost identical for both duct geometries for the common range of Re. An example of the use of the results for simple heat transfer calculations illustrates a problem. The results are valid for a constant-potential/temperature boundary condition.

Coil Heat Exchanger with the Nanofluid Filled Buffer Layer

The paper presents the preliminary design of the special heat exchanger. The device under consideration is the kind of immersed coil heat exchangers. It consists of three vertical coils: two coils are standard, water is used as a heating medium; one coil is filled by the refrigerant R134a which transfers the waste heat from refrigeration and air conditioning system during the boiling processes. In order to prevent the possible refrigerant leakage, the special buffer layer filled with the nanofluid is mounted in the Freon coil. Thermophysical properties of the nanofluid cause the intensification of the heat transfer through the buffer layer and the same increase of the heat transfer rate. Calculations of thermal power were made. Correlations of heat transfer coefficients in curved tubes, pressure drop correlations for flow through helical coil tubes and correlations describing the heat transfer in the buffer layer, were applied. Results of the calculations indicate of the influence of of Freon coil on the exchanger heat transfer rate. Heat power of Freon coil is about 7 – 25% of water coil thermal power. Thus, the waste heat applied significantly increases the exchanger heat transfer rate.