Abstract
INTRODUCTION
A heat exchanger are commonly used in practice, and engineer often finds himself in a position to select a heat exchanger that will archieve a specific teamperature change in a fliud stream of known mass flow rate, or to predict the outlet teamperature of the hot and cold fluid streams in a specific heat
exchanger. In application, heat exchanger is device that efficiently transfers heat from a warmer fluid to a colder fluid. A device we are probably all familiar with is the automobile radiator. Other applications for heat exchangers are found in heating and air conditioning systems. Heat exchangers are categorized in many ways, but the two most common practices are, by the method of construction, and by the flow arrangements. The analysis for designing an effective heat exchanger is very important; after all who'd want to be caught on the side of a deserted desert road with an overheated engine!
After we have learned how to analyze conduction and convection heat transfer in various systems with different geometries. This information, however, is not very useful unless it can be applied to practical situations. For this reason we shall devote this experiment to a prototypical application of heat transfer analysis known as a heat exchanger.
In this experiment we will study a concentric tube heat exchanger with parallel and counter flow. For the analysis of this heat exchanger we will need to find important quantities such as the heat transfer coefficient, power emitted, absorbed, and lost, the log mean temperature difference, and the overall efficiency to compare the two types of flow.
The variables that affect the performance of a heat exchanger are the fluids’ physical properties, the fluids’ mass flow rates, the inlet temperature of the fluids, the physical properties of the heat exchanger materials, the configuration and area of the heat transfer surfaces, the extent of scale or deposits on the heat transfer surfaces, and the ambient conditions.
LITERATURE REVIEW
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another without affecting the other properties of the medium. The medium is separated by a solid wall, so that they can never mix. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petroleum refineries, natural gas processing and sewage treatment.
The hot water is pumped through a pipe to an insulated tube for which heat will be exchanged. The actual heat exchange takes place in the insulated tubing for which cold water flows concentricity around the hot water tube in two different flow arrangements. These two arrangements, parallel and counter flow, can be changed by opening and closing certain valves within the network of hot and cold water tubing. Each flow arrangement is shown on a diagram located on the front panel. It is worthwhile to note that the temperature at cold-in changes to temperature at cold-out when a counter flow arrangement is used. The same situation applies to the temperature at cold-out, which changes to temperature cold-in for the counter flow.
The other readings remain the same. The flow rates can be adjusted for both cold and hot water by turning the valve knobs on the right side of the panel. Thermometers are located at the inlet, exit and middle of the insulated heat exchanger tubing for both hot and cold water.
For efficiency, heat exchangers are designed to maximize the surface area of wall between two walls. In some cases, fin or corrugations will be added to further increase the efficiency.
Tube exchanger
fluids runs over the tubes that are being heated or cooled to act as a exchanger agent.
OBJECTIVE
i) To compare the effectiveness between parallel flow and counter flow heat transfer and choose the most effective.
ii) To study the effect of volume flowrate to the performance of the heat transfer.
Methodology
The test rig is bench-mounted and contained as a unit. This concentric tube heat exchanger in this experiment is able to operate in either parallel flow or counter flow just by simply open and close the valves. The heat exchanger is in U shape 2 pass type. The outer surface of the tubes is insulated. Eight k-typed
thermocouples are installed at the tube of the heat exchanger as the sensors for this experiment. For hot water tube (inner), 2 thermocouples located at the first and second mixing inlet and 2 thermocouples located at first and second mixing outlet, and same configuration for the cold water tube (outer). Thus four different kinds of temperatures will be measured accurately from inlet to outlet for both hot and cold water. At each end of both hot water and cold water tube was installed with flow rate valve controller so that different flow rate can be obtained.This apparatus has a tank with a heater inside to heat water to a
specified temperature. The temperature setting is adjusted at the thermostat on the front panel. Once the water is heated to the desired temperature it is
