Double-pipe Heat Exchanger, oldie but a goodieDescripción completa
Double-pipe Heat Exchanger, oldie but a goodieDescripción completa
HE Double Pipe
double pipe heat exchanger
DPHE
Full description
Double pipe heat exchangerFull description
Heat ExchangerDeskripsi lengkap
Heat exchanger calculation
Double pipe Heat exchangers
Descrição: Lab Report
Lab ReportFull description
Full description
Cross Flow Heat Exchanger Report
Lecture notes for undergraduate students
teknik
Heat exchanger
Abstract: In this experiment we are going to measure the effectiveness, NTU and the overall heat transfer coefficient in a double pipe heat exchanger in two arrangements (counter & parallel flow). We start the test and took the readings of the water entering and leaving the pipes for both hot and cold flow. To find the rate of heat transfer we applied energy balance on the pipes. Then we used the Kay and London law to know the performance of the heat exchanger (effectives & NTU).
Introduction: A heat exchanger is a device used to transfer heat between a solid object and a fluid, a fluid, or or between two or more fluids. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space in space heating, refrigeration, heating, refrigeration, air air conditioning, power conditioning, power stations. Examples of heat exchanger: e xchanger: 1. Double pipe 2. Shell and tube 3. Coil 4. Plate
Apparatus & procedure: 1. After setting up a given configuration (parallel or counter, switch the pump on (hot stream flow). 2. Open the tap cold water valve to initiate the cold stream 3. Set the heater control to the required temperature. Do not exceed 80°C. 4. Allow the water in the tank to stabilize at the set temperature. Monitor the stability of the system through watching the inlet and outlet hot water temperature. 5. Set the mass flow rate of the hot and cold streams, allow the system to stabilize. 6. Record the readings of the temperatures profiles for the hot and cold streams especially the terminal temperature (in and out for both flows) 7. Record the mass flow rates of the two streams (me, mh). The cold water flow rate is calculated as the volume of water passes (read from the water flow meter on the tap water piping per certain period of time (use stop watch). The same thing is valid for the hot stream flow.
Inner Pipe
Outer Pipe Outlet Cold Water valves
Inlet Cold Water
Take readings of temperature from this knob that is
Outlet Hot Water
attached to
Inlet Hot
different
Water
thermocouples
pump
P
Water Tank
We control the flow if parallel or counter by the valves. In our setup we only control cold flow
Discussion: As the area increase in the heat exchanger as the rate of heat transfer increase , this exist in shell and tube heat exchangers because we can add more pipes without taking much space, so they are used in industries. Coil heat exchangers used in refrigeration cycles Plate heat exchanger used in automotive vehicles Heat exchangers wall usually very thin, so the resistance of the conductivity decrease. Our goal is to achieve the highest temperature in the cold flow at exist and the lowest temperature in the hot flow exit. (Max heat transfer wanted) In counter flow > ℎ In parallel flow ℎ ℎ That is because the temperature difference in parallel flow at the e ntrance is very high and will decrease with length, but in counter flow the temperature difference is uniform. This means that thermal stress may occur in parallel flow heat exchanger So why we want parallel flow? It is used in any application which we want to maintain specific temperature.
We usually put the hot stream inside so that is losses the heat to the cold fluid surrounded by it, That means we don’t have to use insulators. (saving money and space)
( ̇ ∗ ) = , ( ̇ ∗ )ℎ = ℎ = The heat capacity ratio If Ch = Cc the cold flow temperature eventually will reach the hot flow temperature If Ch is much bigger than Cc, the hot flow will experience low temp difference due to large mass flow rate
If Ch is much smaller than Cc, the cold flow will experience of low temp difference due to large mass flow rate
Since we have non-linear relationship we used logarithmic mean temperature difference and because we have 4 temperature and we need the average.
Conclusion: As the area increase in the heat exchanger as the rate of heat transfer increase. Heat exchangers wall should be very thin. In counter flow > ℎ In parallel flow ℎ ℎ The maximum heat transfer happen at the lower heat capacity ratio If Cr = 0, it is a special case of heat exchanger which is a condenser or evaporator And = 1 − What the cold water gain, the hot water losses so both Q should be equal but due to human and machines errors.
