The heating is to be accomplished by passing hot engine oil which is at 160 c through the shell side of the exchanger. Heat transfer is a function of reynolds number.
Devices involving energy sources such as nuclear fuel pins or fired heaters are not normally regarded as heat exchangers although many of the principles involved in their design are the same.
Cross flow heat exchanger. For efficiency heat exchangers are designed to maximize the surface area of the wall between the two fluids while minimizing resistance to fluid flow through the exchanger. Dynamic model of a cross flow heat exchanger introduction this article will develop a dynamic model of a cross flow heat exchanger from first principles and then discretize the governing partial differential equation with finite difference approximations. The oil provides an average convection coefficient ho 400 w m2 k on the outside of the tubes.
A heat exchanger is a device used to transfer heat between two or more fluids. A heat exchanger can have several different flow patterns. Crossflow parallel flow and counterflow heat exchanger configurations are three examples.
The fluids can be single or two phase and depending on the exchanger type may be separated or in direct contact. A crossflow heat exchanger is designed so that the two fluids flow perpendicular to one another. See the thermodynamics heat transfer and fluid flow fundamentals for a review of log mean temperature.
In a cross flow heat exchanger the fluids travel roughly perpendicular to one another through the exchanger. This can be seen by comparing the graphs in figure 3 figure 4 and figure 5. 10 1615 atoz c cross flow heat transfer when a fluid flows across a solid object or ensemble of solids at a different temperature crossflow heat transfer results.
Therefore the log mean temperature for a counter flow heat exchanger is larger than the log mean temperature for a similar parallel or cross flow heat exchanger. The simplest heat exchanger is one for which the hot and cold fluids move in the same or opposite directions in a concentric tube or double pipe construction. A shell and tube heat exchanger must be designed to heat 2 5 kg s of water from 15 to 85 c.
A counterflow heat exchanger will require less heat exchange surface area than a parallel flow heat exchanger for the same heat transfer rate and the same inlet and outlet temperatures for the fluids. In the parallel flow arrangement of figure 18 8 a the hot and cold fluids enter at the same end flow in the same direction and leave at the same end. 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.