A new method of determining the convective heat-transfer coefficient
. Energy Res.
Until now, the cooling channels were assumed to have a uniform heat-transfer coefficient
throughout the mold.
NOMENCLATURE A = heat transfer area or area of cross-section, [m.sup.2] D = diameter, m Gz = Graetz number, DRePr/L, dimensionless h = heat-transfer coefficient
, W [m.sup.-2] [K.sup.-1] L = fiber length, m N = number of fibers, dimensionless Nu = Nusselt number, hD/k, dimensionless Pr = Prandtl number, [C.sub.p][mu]/k, dimensionless Q = rate of heat transfer, W R = thermal resistance, [m.sup.2] K [W.sup.-1] Re = Reynolds number, Du/[mu], dimensionless T = temperature, K [DELTA]T = temperature difference, K U = overall heat-transfer coefficient
, W [m.sup.-2] [K.sup.-1] Subscripts f = frontal i = inner o = outer ov = overall t = tube T3 = convection boundary condition (the third type) w = wall ACKNOWLEDGMENTS
In addition, because the NTU is inversely proportional to the Re, it follows that a small improvement in the overall heat-transfer coefficient
would be accompanied by a decrease of the NTU and the efficiency.
Nenad Miljkovic, a doctoral student at the university, and colleagues in the device research laboratory, have designed a surface coating that has an increased heat-transfer coefficient
In a similar manner, the effect of heat transfer is the heat-transfer coefficient
, which is defined as the quantity of heat passing through a unit area of material, of a unit thickness, in a specific unit of time, when one side differs by 10 Kelvin.
Purdue University researchers have shown that the technology increased the heat-transfer coefficient
, which describes the cooling rate, by as much as 250 percent.
The software can be used to compute flow rate, pressure drop, and heat-transfer coefficient
in fluid transport devices.
This gives you the overall heat-transfer coefficient
, which is the heat transfer between the polymer and the cooling medium.
Users plug in the profile shape and material, and the computer simulates the cooling time needed by calculating the convection heat-transfer coefficient
from the profile into the coolant, while taking into account how profile mechanical properties are impacted by specific cooling times.
Then there is a heat-transfer coefficient
for the "gap" between the polymer and the roll surface.