Z. Lipnicki

Role of the contact layer between liquid and solid on a solidification process

Abstract The object of this paper is the presentation of a theoretical solidification model of heat-conducting liquid metal flowing near of a cold plate. The problem of the unsteady behaviour both of the frozen metal layer and of the cold plate is studied analytically. Influence of the contact layer between the frozen layer and the cold plate on the solidification process is also studied. The results in the form of the analytical formula and the graphs are presented and compared with the other results.

Natural convective flow between an array of vertical cylinders

Abstract The natural-convectioe flow of a viscous and heat-conducting fluid in systems of cylinders, arranged vertically in regular patterns, is studied. The aim of the study is to determine the conditions of stability of the fluid when heated from below and cooled from above. In particular, the influence of geometry and thermal properties of the system on the free stationary convection are studied. A new way of calculating the free convection threshold is proposed. The final results are analytical formulas for determining the critical Rayleigh numbers for the studied forms of flow and graphs, showing the dependency of these numbers on the geometrical parameters of arrays.

Heat Transfer and Temperature Distribution Outside the Borehole

In this paper a theoretical analysis of the non-stationary distribution of temperature outside a borehole in the ground is presented. The ground, surrounding the cylinder, is the source to heat or cool the medium flowing inside the cylinder. Direction of temperature distribution in the ground depends on the circumstance if the cylinder is responsible for heating or cooling. The discussion will concern the effect of an accumulation of heat in time by the deposit (ground) and the distance from the borehole to the place where there is no heat exchange, as well as the influence of temperature distribution on cooling or heating effects. An analytical model was designed to determine a profile of temperature in the ground and the Nusselt number in the borehole dependents on both the time and the outward radius. An attempt is made to define the radius of the thermal influence of the.Copyright

Dynamical solidification of metal filling a cooled cylindrical channel

The paper examines theoretically the solidification of a viscous and heat-conducting liquid filling a cooled cylindrical channel. Changeable amount of liquid takes part in the motion. It is contained between the frontal area of the stream moving with the liquid and the solidification interface. The flow of the liquid is treated as a Poiseuille flow. The paper discusses the influence of the cooling conditions as well as the conditions of the flow on the solidification process.

Cooling of a Processor With the Use of a Heat Pump

Abstract In this paper the problem of cooling a component, in the interior of which heat is generated due to its work, was solved analytically. the problem of cooling of a processor with the use of a heat pump was solved based on a earlier theoretical analysis of authors of external surface cooling of the cooled component by using the phenomenon of liquid evaporation. Cases of stationary and non-stationary cooling were solved as well. The authors of the work created a simplified non-stationary analytical model describing the phenomenon, thanks to which heat distribution within the component, contact temperature between the component and liquid layer, and the evaporating substance layer thickness in relation to time, were determined. Numerical calculations were performed and appropriate charts were drawn. The resulting earlier analytical solutions allowed conclusions to be drawn, which might be of help to electronics engineers when designing similar cooling systems. Model calculations for a cooling system using a compressor heat pump as an effective method of cooling were performed.

Solidification in an Annular Space

The outer geometry of PCMs built of concentric annuli can be also used for heat storage because of their relatively large outer surface.

Phase Heat Accumulator

The model of a phase heat accumulator presented in this chapter is based on the description of both the heat flow and the construction of this unit (Lipnicki and Krasowski 2011; Lipnicki and Krasowski in Uklad pracy akumulatora ciepla, Polska, Nr 39 1082, 2014—patent).

Solidification of a Liquid Flowing into the Channel

The literature on the solidification of a liquid flowing into the channel was reviewed by Cheung and Epstein (1984), Fukusako and Yamado (1994) as well as Weigand et al. (1997, 1999). Experimental research verified by the former theoretical results was conducted by Lipnicki and Weigand et al. (Lipnicki 1996, Weigand 1996; Lipnicki et al. 2009).

Role of the Contact Layer in a Solidification Process

In the theoretical research, the thermal resistance of the contact layer was until now considered a constant parameter in equations defining a liquid solidification of value assumed a priori, and its effect on the phenomenon was investigated posteriorly.

Solidification of PCMs

Heat storage is a subject of considerable importance in power engineering. The most common methods of heat storage exploit the thermal capacity, the latent heat, the heat of reaction and of photo chemical reaction and production of fuels. This work is concentrated on heat storage by exploiting the phenomenon of solidification as a special case of numerous phase changes occurring in reality.