When is heat released from a system a positive quantity?
Heat released by a system into its surroundings is by convention a negative quantity ( Q < 0 ); when a system absorbs heat from its surroundings, it is positive ( Q > 0 ). Heat transfer rate, or heat flow per unit time, is denoted by
How is heat transferred from place to place?
In convection heat transfer, the heat is moved through bulk transfer of a non-uniform temperature fluid. The third process is radiation or transmission of energy through space without the necessary presence of matter. Radiation is the only method for heat transfer in space.
Which is an introduction to engineering heat transfer?
Introduction to Engineering Heat Transfer These notes provide an introduction to engineering heat transfer. Heat transfer processes set limits to the performance of aerospace components and systems and the subject is one of an enormous range of application.
Which is the correct notation for heat transfer rate?
Heat transfer rate, or heat flow per unit time, is denoted by Q ˙ {displaystyle {dot {Q}}} . This should not be confused with a time derivative of a function of state (which can also be written with the dot notation) since heat is not a function of state.
What are the main objectives of heat exchanger calculations?
In process calculations, the main objectives of heat exchanger calculations are to determine the heat duty (amount of energy to be transferred), temperature changes within the exchanger, and pressure drops. Depending on the degree of details available/needed, the calculations might be simple or thorough.
What are the different types of heat exchangers?
There are many types of heat exchangers applied in the process industry. These types include: 1. Hairpin/Double pipe exchangers 2. Shell and tube exchangers 3. Plate and frame exchangers 4. Plate-fin exchangers 5. Spiral heat exchangers 6. Air coolers and condensers 7. Direct contact (quenching towers) 8.
When to use correction factor in heat exchanger?
The correction factor is used in conjunction with the LMTD to account for the deviation from the ideal counter-current flow pattern. For example, shell and tube exchangers where the tubes make more than one pass or when two or more shells are used, as shown in Figure 44.
Where does the exchange of energy take place?
The exchange can take place between a process stream and a utility stream (cold water, pressurized steam, etc), a process stream and a power source (electric heat), or between two process streams resulting in energy integration and reduction of external heat sources.