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Heat Exchanger

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  1 ABSTRACT. Heat exchanger is a device that built for efficient heat transfer from one medium to another. There are two type of flow in double pipe heat exchanger that is counter-flow and co-current flow. Both hot and cold fluids enter the heat exchanger at the same end and move in the same direction in parallel flow (co-current). On the other hand, the hot and cold fluids enter the heat exchanger at opposite ends and flow in opposite directions in counter flow. The heat exchanger also affected by hot water temperature inlet and the flow rate variation. Hot water taken from the pump are discharge while the cold water is taken from the pipe. Both hot and cold water passes through along the concentric tube and the experiment of counter and co-current was carried out. On the panel, the stabilized temperatures that appear were taken.  2 TABLE OF CONTENTS.  Abstract 1 Table of content 2 1.0 Introduction 3 2.0 Objectives 5 3.0 Theory 6 4.0 Diagram and Description of Apparatus 9 5.0 Experimental Procedures 11 6.0 Result and Discussions 13 7.0 Sample Calculation 18 8.0 Conclusions and Recommendations 21 9.0 References 23 10.0 Appendices 24  3 1.0 INTRODUCTION. Heat exchanger is an equipment built for efficient heat transfer from one medium to another. Different applications of heat exchanger require different types of hardware and configurations of heat transfer equipment. There are several types of heat exchanger such as double pipe heat exchanger, compact heat exchanger, shell-and-tube heat exchanger and plate and frame heat exchanger. In this experiment, double pipe heat exchanger was the only apparatus are used. Heat exchangers are a device that exchanges the heat between two fluids of different temperatures that are separated by a solid wall. The temperature gradient or the differences in temperature facilitate this transfer of heat. Transfer of heat happens by three principle means: radiation, conduction and convection. In the use of heat exchangers radiation does take place. However, in comparison to conduction and convection, radiation does not play a major role. Conduction occurs as the heat from the higher temperature fluid passes through the solid wall. To maximize the heat transfer, the wall should be thin and made of a very conductive material. The biggest contribution to heat transfer in a heat exchanger is made through convection. Double-pipe heat exchanger is the simplest type of heat exchanger consists of two concentric pipes of different diameter. One fluid in a double-pipe heat exchanger flows through the smaller pipe while the other fluid flows through the annular space between the two pipes. Two types of flow arrangement are possible in a double-pipe heat exchanger is in parallel flow (  4 co-current ) or counter flow. In parallel flow (co-current), both hot and cold fluids enter the heat exchanger at the same end and move in the same direction. In counter flow, on the other hand, the hot and cold fluids enter the heat exchanger at opposite ends and flow in opposite directions. The performance of heat exchanger usually deteriorates with time as a result of accumulation of deposits on heat exchanger surfaces. The layer of deposits represents additional resistance to heat exchanger and cause the rate of heat transfer in a heat exchanger to decrease. The net effect of these accumulations on heat transfer is represent by a fouling factor R f  , which is a measure of the thermal resistance introduced by fouling. The most common type of fouling is the precipitation of solid deposits in a fluid on the heat transfer surfaces. This type of fouling can be notice by a layer of calcium-based deposits on the surfaces at which boiling occurs. This is especially the case in areas where the water is hard. The scales of such deposits come off by scratching, and the surfaces can be cleaned of such deposits by chemical treatment. Another form of fouling, which is common in the chemical process industry, is corrosion and other chemical fouling. This form of fouling can be avoided by coating metal pipes with glass or using plastics pipes instead of metal ones. Heat exchanger may also be fouled by the growth of algae in warm fluids. This type of fouling is called biological fouling and can be prevented by chemical treatment. The fouling factor depends on the operating temperature and the velocity of the fluids, as well as the length of service. Fouling increases with increasing temperature and decreasing velocity. They are widely used in space heating, refrigeration, air
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