Coolant laminar flow

For laminar flow in the coolant jacket, the overall heat-transfer coeflicient... 

Another important consideration in cooling channel design is to ensure that the coolant circulates in turbulent rather than laminar (streamline) flow. The coefficient of heat transfer of the cooling system is drastically reduced in laminar flow. The condition of laminar or turbulent flow is determined by the Reynolds number (Re). This is a dimensionless number given by the equation ... 

The data from the experiments showed that the overall heat transfer coefficient (for the whole absorber) varied from a minimum of 133 W/m -K at a concentrated solution flow rate of 0.0106 kg/s to a maximum of 403 W/m -K at 0.0361 kg/s. A relatively constant, high value of the coolant-side heat transfer coefficient, 2600 W/m -K, was seen for all the cases tested, in which the flow remains laminar. The absorber was found to be solution-side limited. Heat transfer rates as high as 16.2 kW, representative of residential heat pumps, were achieved in this small envelope however, the performance was somewhat lower than that predicted by the preliminary model of Garimella [34], The 21% smaller surface area of the prototype [37] compared to the modeled design [34] accounted for some of the discrepancy. Also, the single-pressure absorber test facility used in the experiments supplied vapor to the absorber at conditions representative of desorber outlet conditions (as 86.7% NH3) rather than evaporator... 

For prediction of subassembly coolant flow rate and temperature distributions a wide range of coolant flow and thermal convection regimes must be considered including laminar and turbulent flow natural, forced and mixed (forced + natural) convection and steady state and transient reactor conditions. 

More detail of the cross-plane (y - z) geometry is shown in Figure 9.2 (also not to scale). The high aspect ratio of a unit cell suggests the following dimensional reduction That the x direction transport is dominated by the gas channel and coolant flow. Furthermore, since the flow is slow enough to be laminar, these flows can be described simply with average quantities in the x direction. This leads to a 2 -I-1 D model, in which the cross-plane (y-z) problem can be solved for each x and connected to 1-D models for the channel flow. 

Heat transfer drops off> rate than expected and Ap increases faster than expected fouling because of oversized kettle reboiler on distillation column or change in pH or flow regime laminar when design was turbulent or higher level of contamination in fluids or crud carry over from upstream equipment (e.g. silica from catalyst in upstream reactor) or compensation for oversize by reduced coolant flow-rate. 

One possible automotive improvement would be a radiator based on hollow fibers. Such a device offers a huge surface area per volume, and hence a smaller, lighter radiator for the same job. However, because of the small diameter of the hollow fibers, coolant flow will be laminar. Use your knowledge of interfacial transport to suggest appropriate correlations for the overall heat transfer coefficient in such a device. 

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