The role of probable uncertainty in the design and testing of compact heat exchangers

Numerical models are presented for the derivation of probable uncertainties in the design and testing phases of compact heat exchangers. Uncertainty theory is reviewed, particularly for the calibration of instruments to establish acceptable parameters during tests. Probable uncertainty is defined as the entire error due to all causes, and gives a scatter band of error, usually meaning 20:1 odds for retail instruments. Primary uncertainties in compact heat exchangers are obtained for basic flow friction, heat transfer data, and fluid thermal and transport property data. The principle concern is to establish an effectiveness and pressure loss characteristic as a function of mass flow rate. Examples are provided for an off-highway equipment gas turbine recuperator and a series system consisting of a thermocouple, extension wire, and circular dial for a cold outlet plate.