# Concentric Tube Heat Exchanger

Topics: Log mean temperature difference, Heat exchanger, Heat transfer Pages: 11 (2580 words) Published: February 6, 2013
OBJECTIVE
The main purpose of this experiment is:-
i. To demonstrate the working principles of industrial heat exchangers ii. To investigate the efficiency of the heat exchanger in parallel and counter flow arrangements 1.0 INTRODUCTION
A heat exchanger is equipment in which heat exchange takes place between 2 fluids that enter and exit at different temperatures. The main function of heat exchanger is to either remove heat from a hot fluid or to add heat to the cold fluid. The direction of fluid motion inside the heat exchanger can normally categorised as parallel flow, counter flow and cross flow. For parallel flow, also known as co-current flow, both the hot and cold fluids flow in the same direction. Both the fluids enter and exit the heat exchanger on the same ends. For counter flow, both the hot and cold fluids flow in the opposite direction. Both the fluids enter and exit the heat exchanger on the opposite ends. Examples in practice in which flowing fluids exchange heat are air intercoolers and preheaters, condensers and boilers in steam plant, condensers, condensers and evaporators in refrigeration units, and many other industrial process in which a liquid or gas is required to be either cooled or heated. Heat exchanger works as hot water and cold water enters the exchanger, where the process of cold water gaining some heat and the hot water losing some takes place, before they both exit the exchanger. What is actually happening is, the hot water is heating either the inside or the outside of the tubes in the exchanger, depending on where it is flowing, by what is known as convection. Then the heat is conducted through the tubes to the other side, either the outside or the inside, where it is then convected back into the cold water raising its temperature. Convection is a mode of heat transfer that involves motion of some fluid that either absorbs heat from a source or gives heat to some surrounding. Conduction is a mode of heat transfer in which the heat is moving through a stationary object or fluid. For a heat exchanger that flows parallel or counter current then the coefficient of heat transfer is called the overall coefficient of heat transfer. It is calculated using the log mean temperature difference, which is found two different ways, depending on whether the flow is parallel or counter. 2.0 MATERIALS AND APPARATUS

Concentric tube heat exchanger
PROCEDURE
PART A – Parallel Flow Heat Exchanger
1. The circulation of cold water started.
2. The flow of cold water was set to parallel to the flow of hot water. 3. The main switch and the pump were switched on.
4. The temperature controller was set to 60°C.
5. The hot water flow rate was set to 2 L/min and the cold water flow rate to 1.5 L/min. 6. The temperature enabled to stabilize before recording the temperatures from T1 to T6.

PART B – Counter Flow Heat Exchanger
1. The temperature controller was set to 60°C, and the hot water flow rate and cold water flow rate to 2 L/min and 1.5 L/min respectively. 2. Upon reaching steady-state conditions, the temperature readings from T1 to T6 were recorded. PART C – Flow Rate Variation

1. A counter flow set up was used on the heat exchanger.
2. The temperature controller was set to 60°C.
3. The cold and hot water flow rate were set to 2.0, 3.0, 4.0 and 5.0L/min.

PART D – Water Temperature Variation
1. A counter flow set up was used on the heat exchanger.
2. Both the cold and hot water flow rate were set to 2L/min. 3. The hot water temperatures were varied to 50°C, 55°C and 60°C. 4. Upon reaching steady-state conditions, the temperature readings from T1 to T6 were recorded.

3.0 RESULTS AND DISCUSSION

PART A – Parallel Flow Heat Exchanger

Readings| TT1( tHin )°C| TT2( tHmid )°C| TT3( tHout )°C| TT4( tCout )°C| TT5( tCmid )°C| TT6( tCin )°C| | 59.2| 54.8| 51.2| 38.4| 35.3| 28.7|
Calculations| PoweremittedW| PowerabsorbedW...