Plate Heat Exchanger

Heat transfer
Heat transfer is the science of estimating the transfer of energy caused by the temperature difference between objects or material. Studies of heat transfer explains how energy moves from one object to another object by estimating the rate of displacement that occurs in certain conditions.(Holman, 1986)

Convection Heat Transfer in Pipe
Heat transfer involving liquid or gas in the heat exchanger, heat transfer by convection is equal to the heat transfer by conduction.

In the industrial process, generally hot fluid moving from one heading to another after the fluid through a solid wall. Figure A shows that the heat goes out of the flow of hot fluid to cold fluid flow with a temperature profile.

In the turbulent fluid flow, the velocity gradient between the flow in the bulk section of the thin viscous sublayer is located near the walls are very high. In this case, the conduction heat transfer arise with high temperature difference that is from T2 to T3 (part of hot fluid). After much pass through the wall, and are nearing the turbulent, the temperature is reduced and the difference T1 and T2 to be small because the movement arises Eddy style. The average temperature of the hot fluid film layer is smaller than the temperature at the T1 bulk. It can also be explained to the temperature profile in the cold water.

Type of fluid flow, laminar or turbulent has a great influence terhaadap convection heat transfer coefficient (h), where the heat transfer constraints found in the thin film layer close to the wall. The more turbulent the flow, the greater the heat transfer coefficient konveksinya.

Correlation coefficients to predict the price of a movie (h) is influenced by the physical properties of the fluid, the type and flow rate, temperature difference and the geometry of the system physics. (Geankoplis, 1983)

Heat exchanger
Heat exchanger is a tool to implement the transfer of thermal energy from one fluid to another fluid. In the simplest heat exchanger, the hot fluid and cold fluid mix directly whereas in most of the other second heat exchanger fluid are separated by a wall. This type of heat exchanger, called rekuperator, it may just be a simple flat wall that separates the two fluid flow, but might also be a complex configurations involving cross-cross double, fins, or bulkhead. In this case, the necessary principles of conduction and convection heat transfer, sometimes also radiation, to give prosos energy exchange.


Jenis-jenis penukar kalor.
 Types of heat exchanger types of heat exchanger which is common among other types of plate-flat (flat-plate), sleeves and tubes (shell and tube) and the type of cross flow (crossflow). Examples of the double pipe heat exchanger (double pipe exchanger), which is one of the simplest forms of shell and tube, seen in Figure b. if both the fluid flowing in the same direction, as in the picture, then a heat exchanger that includes parallel flow type (parallel flow); if the second fluid flows in the opposite direction, then it is called a heat exchanger opponent genres directions (counterflow). (R.Pitts dan E.Sissom,1987)

Plate Heat Exchanger (PHE)
PHE is a means of heat transfer by plate-shaped frame as barriers. No heat transfer occurs through plate-plate which serves as the conductor insulation. Excess PHE other than HE is the heat transfer surface area greater with the same amount of fluid, so in terms of pinch analysis, it is more advantageous because heat transfer occurs more efficiently. In terms of manufacturing, it is advantageous because it does not need a place that is too broad.

Struktur sederhana dari PHE

PHE can be used in industries that produce food ingredients due to temperature and operating pressure is not too large so as not to damage groceries. (www.cepmagazine.org)


Calculation of heat exchanger
The main target is to design a heat exchanger to determine how the surface area required to remove heat at a certain rate with the temperature of the liquid and a certain flow rate. It would be easier if we use the overall heat transfer coefficient (U) in the fundamental equation of heat transfer.

q = U.A.dT lmtd

where dT lmtd is the temperature difference average effective for the entire heat exchanger.

Factors Impurities
Performance depends on the surface of the heat exchanger for heat transfer was clean or not. If there are deposits on the surfaces, thermal prisoners will be increased, so that his performance would be reduced. Additional prisoners are usually taken into account as fouling factor (fouling factor). Fouling factor determined experimentally by testing a heat exchanger that is clean and dirty state is defined as follows:

Rd = (1/Ud)-(1/Uc)
(R.Pitts dan E.Sissom,1987)

Source:

Geankoplis, J.C, 1993, �Transport Processes and Unit Operations� 3^rd edition, Prentice Hall, New Delhi

Holman, J.P , �heat transfer�, ed.keenam, Erlangga, Jakarta

Kern, Donald, 1965, � process Heat Transfer�, Mc.Graw Hill International edition, Singapore

R.Pitts and E.Sissom, 1987, �heat transfer�, Erlangga, Jakarta

(www.cepmagazine.org)