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A numerical approach is developed for local thermal stress assessment in occupied built environments. A CFD airflow model is coupled with a human thermoregulation model to simulate the basic environmental parameters with having regard to the occupant body heat rejection and moisture emission. Effective temperature (ET) and wet bulb globe temperature (WBGT) are used as the heat indices for indoor thermal stress assessment. Algorithms for computation of three dimensional (3-D) distributions of the heat indices are established, so that local thermal stress levels at certain locations in the environment can be predicted and evaluated according to the simulation results of the basic parameters. A demonstrative analysis for a crowded rectangular space with mechanical ventilation is given.

A thermodynamic model with a novel method of describing the performances of centrifugal chillers for air-conditioning is presented. It is based on the first and second laws of thermodynamics which captures the overall entropy change due to non-isentropic compression and expansion of the thermodynamic cycle. The model gives the fundamental relation between the coefficient of performance (COP) and the cooling rates (Qe) for (a) the modulating and (b) the throttling actions of the inlet guide-vanes of the compressor. The usefulness and the accuracy of the model are demonstrated here by analysing the in situ performance of two commercial, installed centrifugal chillers of an air-conditioning plant as well as comparing the available performance data of another chiller in the literature.

The paper examines the thermodynamic processes of a helical screw-expander that operates with dry saturated steam at its inlet. The work output of the screw-expander is analysed using a simple ‘pseudo-polytropic’ index. Using the available experimental data from the literature, an empirical model for the prediction of work using the ‘pseudo-polytropic’ indices is formulated. The expansion indices are expressed in terms of built-in volumetric and pressure ratios; how they are formulated is usually given in an expander specification. Based on the empirical model, there is a good agreement between the experimental work and the predicted values.

Recent changes in federal and state requirements have resulted in the classification of backwash water from water‐purification plants as a potential pollutant that requires treatment before disposal. This article attempts to determine the effects of backwash‐water recycling on the filter operation and the plant effluent quality.

An experimental investigation was conducted to determine the void fraction and pressure drop occurring in a forced-convection water electrolysis cell. It was concluded that the slip ratio is essentially unity for water electrolysis cells operating at atmospheric pressure and 80–100 deg F. A frictional pressure-drop multiplier was determined by a data reduction technique that has been used extensively in the boiling heat transfer literature. This multiplier has been correlated and found to be a function of both the void fraction and the gas generation rate.