#BODY HEAT MOVIE MEANING FREE#
Through rigorous experimental tests of free convection with various fluids (both liquids and gases) flowing past horizontal cylinders and vertical plates, the exponents a and b have been found to be numerically same. The basic equation developed from dimensional analysis for use in determining the value of convection coefficient h is. The local and average convection coefficients are related by an expression of the form,įor the usual free convection circumstances, the following dimensionless numbers apply: Q x = h x dA (t s – t ∞) = K (B dx) (t s – t ∞) …. However for an elementary strip of length dx located at a distance x form the leading edge, the convective coefficient can be assumed to be practically constant. The flow conditions vary from point to point on the surface, and as such the convective film coefficient and the heat flux would also vary along the surface.
If temperature t s at the plate surface is greater than the free stream temperature t ∞then convective heat transfer occurs from the plate to the fluid. 10.1 where a fluid with velocity U ∞ and temperature t ∞ flows past a stationary flat plate of length l and width B. Local and Average Convective Coefficient :Ĭonsider the flow condition depicted in Fig. The mean film temperature t f is the arithmetic mean of the surface temperature t s of a solid and the undisturbed temperature t ∞of the fluid which flows past it t f = (t s + t ∞)/2. The bulk temperature is then taken to be the arithmetic mean of the temperatures at inlet to and at exit from the heat exchanger tube, i.e., t b = (t i + t a)/2. In heat exchangers, the fluid flowing through the tubes may be heated or cooled during its flow passage. For turbulent flow of fluids in ducts, this temperature is very nearly equal to the fluid temperature near the duct axis. The mean bulk temperature t h denotes the equilibrium temperature that would result if the fluid at a cross-section was thoroughly mixed in an adiabatic container. However, it is customary to evaluate the fluid properties either on the basis of bulk temperature or the mean film temperature. No uniform procedure has been attained in the selection of this reference temperature. Undoubtedly the accuracy of the results obtained by using theoretical relations and the dimensionless empirical correlations would depend upon the temperature chosen for the evaluation of these properties.
The physical properties (µ, k, ρ, c p) of a fluid are temperature dependent. Bulk Temperature and Mean Film Temperature :
#BODY HEAT MOVIE MEANING FOR FREE#
In this article we will discuss about the empirical correlations for free and forced convection.