Thermoeconomics is a blend of thermodynamics with economics. The thermodynamic analysis uses the second law and the concept of exergy, the measure of usefulness of energy. Economics involves costing exergy flows in life costing techniques. The objective of thermoeconomics is to minimise a cost function, talcing into account capital, maintenance and running costs. Most of these are expressed in terms of thermodynamic variables of the system. This will establish the most cost effective design parameters.
Mechanical ventilation of workrooms was formerly based mainly on the dilution principle. In recent years, however, 50% of new investments in industrial ventilation in Scandinavia have been spent on displacement ventilation. Very little data exist from industrial settings on the relative performance of displacement ventilation versus dilution ventilation as regards air quality and thermal comfort. The present study collected data on the indoor climate in a sewing plant before and after the ventilation was changed from dilution to displacement.
Personal exposure in a displacement ventilated room is examined. The stratified flow and the considerable concentration gradients necessitate an improvement of the widely used fully mixing compartmental approach. The exposure of a seated and a standing person in proportion to the stratification height is examined by means of fullscale measurements. A breathing thermal manikin is used to simulate a person. It is found that the flow in the boundary layer around a person is able to a great extent to entrain and transport air from below the breathing zone.
Login