A model has been developed to predict the latent capacity of an air conditioner or heat pump at part-load conditions with a continuously operating supply fan. The model predicts the latent heat ratio (LHR) at part-load conditions as a function of the run-time fraction (X) or cooling-load fraction (CLF). The model parameters necessary to quantify system performance include the maximum cycling rate, the air-conditioner time constant, the ratio of the initial evaporation rate and steady-state capacity, the nominal time after start-up for condensate removal to begin, and the temperature and humidity entering the coil. The model compared favourably to measured data from Khattar et al. (1985). A sensitivity analysis was conducted to determine the model parameters that have the strongest impact on the part-load LHR. The model can be easily integrated into hourly building simulation models to more accurately predict the dehumidification performance of air conditioners at part-load conditions.

KEYWORDS: year 1996, calculating, capacity, unit air conditioners, heat pumps, part load, latent heat, ratios, cooling load, performance, accuracy, dehumidifying