What is LMTD in heat exchanger?
1. The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger.
What do you mean by LMTD & NTU method?
The Number of Transfer Units (NTU) Method is used to calculate the rate of heat transfer in heat exchangers (especially counter current exchangers) when there is insufficient information to calculate the Log-Mean Temperature Difference (LMTD).
What is the difference between LMTD and NTU method?
The LMTD method is convenient for determining the overall heat transfer coefficient based on the measured inlet and outlet fluid temperatures. The ε-NTU method is more convenient for prediction of the outlet fluid temperatures if the heat transfer coefficient and the inlet temperatures are known.
Why we use LMTD method in heat exchanger?
Heat exchangers are usually analyzed using either the Logarithmic Mean Temperature Difference (LMTD) or the Effectiveness – Number of Transfer Units (ε-NTU) methods. The LMTD method is convenient for determining the overall heat transfer coefficient based on the measured inlet and outlet fluid temperatures.
What is the LMTD for a heat exchanger?
U is the overall heat transfer coefficient for that exchanger A overall is the overall effective heat transfer area between the hot and cold sides of the exchanger LMTD is the logarithmic mean of temperature differences as discussed above.
What does logarithmic mean temperature difference ( LMTD ) mean?
Logarithmic Mean Temperature Difference (LMTD) is an indicator of the average temperature difference between the hot and cold fluids in a heat exchanger. As can be seen from the equation, LMTD uses the logarithmic mean of the temperature differences instead of an arithmetic mean.
What is the log mean temperature difference in a heat exchanger?
The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold streams at each end of the exchanger.
Which is the best example of a LMTD?
The easiest way to look at the LMTD is as a comparison of the two fluid’s temperatures throughout the exchanger. Since most exchangers are counter-current, comparing either end of the exchanger gives a simplified example of the LMTD. This would be the hot outlet and cold inlet, or the cold outlet and hot inlet.