What is counter flow heat exchanger?
A counter-flow heat exchanger is one in which the direction of the flow of one of the working fluids is opposite to the direction to the flow of the other fluid. Second, the temperature of the cold fluid exiting the heat exchanger never exceeds the lowest temperature of the hot fluid.
How does a cross flow heat exchanger transfer heat?
A crossflow heat exchanger is designed so that the two fluids flow perpendicular to one another. This is typically utilized when one fluid is a liquid and the other is a gas, as in a car radiator in which hot water flowing left and right is cooled by air moving up or down, Bright Hub Engineering explained.
What is the efficiency of a heat exchanger?
The heat exchanger efficiency is defined as the ratio of the actual rate of heat transfer in the heat exchanger, q, and the optimal rate of heat transfer, qopt,(1) η = q q opt = q U A ( T ‾ – t ¯ ) The optimum (maximum) rate of the heat transfer is the product of UA of the heat exchanger under consideration and the …
How can the efficiency of a heat exchanger be improved?
Heat transfer coefficient, pressure drop, baffles and fouling are responsible for the efficiency of the heat exchanger. By increasing the flow resistance the heat transfer rate can be increased by creating the turbulence in the shell side of the heat exchanger.
How does flow rate affect heat exchanger?
In other words, the rate of heat transfer is directly proportional to mass flow rate. If you increase the flow rate, you will then increase the rate of heat transfer. Then, from the relationship above, increasing the mass flow rate must result in a smaller delta T because Q remains constant.
Does turbulent flow increase heat transfer?
The heat transfer coefficient increases when the fluid velocity increases (better mixing in the turbulent boundary layer, thinner laminar su-blayer). A turbulent flow increases the amount of air resistance and noise; however, a turbulent flow also accelerates heat conduction and thermal mixing.
Does pressure change in a heat exchanger?
Pressure is NOT constant in heat exchangers, because fluid flow always leads unavoidably to pressure drop as an effect of fluid friction. Therefore, you can calculate the thermodynamic properties of the fluids at a constant absolute pressure, even in the case of gases.
How do you reduce pressure in a heat exchanger?
Tube side pressure drop can be lowered in following ways: Increasing the shell diameter. Increasing the shell diameter increases tube flow area due to increased number of tubes and, thereby, reduces tube flow velocity and, hence, reduces tube side pressure drop.