- Author
- Johannesson, G.
- Title
- Heat Flow Measurements, Thermoelectrical Meters, Function Principles, and Sources of Error.
- Coporate
- Lund Univ., Sweden
- Report
- LUTVDG/TVBH-049; TUBH-3033, 1979, 2 p.
- Keywords
- heat flow | flow measurement | measuring instruments
- Abstract
- By using an analytical relation between the heat-flow and harmonic temperature oscillations at the surface boundary the error in measured heat resistance is derived as a function of the time passed from the beginning of the measurement. At a certain frequency expressions for the maximal error are given as a function of the thermal properties of the construction, the initial state, the temperature amplitude at the construction boundaries and the mean temperature difference over the construction. From those expressions the influence of the different factors can be estimated. An interesting result is that, independent of the initial state, the maximal error alwasy occurs after n + 1/2 periods and the minimal error after n periods if n is an integer. This implies that if one dominating frequency component such as the 24-hour cycle is known the error because of this freuqency component can be minimized by measuring through a whole number of periods.