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The heat transfer coefficient is often calculated from the Nusselt number (a dimensionless number). There are also online calculators available specifically for Heat-transfer fluid applications. Experimental assessment of the heat transfer coefficient poses some challenges especially when small fluxes are to be measured (e.g. < 0.2 W/cm 2). [1] [2]
The LMTD is a logarithmic average of the temperature difference between the hot and cold feeds at each end of the double pipe exchanger. For a given heat exchanger with constant area and heat transfer coefficient, the larger the LMTD, the more heat is transferred.
This coefficient accounts for the time lag between the outdoor and indoor temperature peaks. Depending on the properties of the building envelope, a delay is present when observing the amount of heat being transferred inside from the outdoors. The CLF is the cooling load at a given time compared to the heat gain from earlier in the day. [1] [5]
The number of transfer units (NTU) method is used to calculate the rate of heat transfer in heat exchangers (especially parallel flow, counter current, and cross-flow exchangers) when there is insufficient information to calculate the log mean temperature difference (LMTD). Alternatively, this method is useful for determining the expected heat ...
This increases to 3.57 with a heat transfer surface temperature of 100 °C (212 °F) (viscosity 2.82 × 10 −4 Pa.s), making a significant difference to the Nusselt number and the heat transfer coefficient.
The Stanton number, St, is a dimensionless number that measures the ratio of heat transferred into a fluid to the thermal capacity of fluid. The Stanton number is named after Thomas Stanton (engineer) (1865–1931). [1] [2]: 476 It is used to characterize heat transfer in forced convection flows.
Diagram showing components and mechanism for a heat pipe containing a wick Heat pipes keep ground frozen and inhibit water transfer into the open pit during mining activities at Ekati Diamond Mine This 100 mm by 100 mm by 10 mm high thin flat heat pipe (heat spreader) animation was created using high resolution CFD analysis and shows temperature contoured flow trajectories, predicted using a ...
Heat transfer may be a result of a constant heat flux or constant surface temperature. Constant heat flux may be caused by joule heating from a heat source, like heat tape, wrapped around the pipe. [13] Constant temperature conditions may be produced by a phase transition, such as condensation of saturated steam on a pipe surface. [14]