Performance Analysis of a Combined Heat Pump-Dehumidifying System

During the past few decades, all Gulf States have experienced a rapid growth in living standard, which was naturally associated with rapid increase in demand for electricity and potable water. Due to changes of living style, large portion of the electric power was consumed for air conditioning (A/C). Lack of natural water resources and striving needs for water made desalination the main technology to provide potable water. In an effort to search for a novel method for producing fresh water, the present paper investigates a combination of a heat pump (HP) with a dehumidification process to extract water from the atmospheric air. The unit supplies 1.586 m 3 /s air to an office building (250 m 2 area) by the sea side in Jeddah, Kingdom of Saudi Arabia (KSA) where the average ambient temperature is 34 o C and relative humidity of 71%. The unit has two series evaporator-coils to maximize the water condensation process by reducing the air exit temperature to 8 o C. The performance of the combined HP-Dehumidifying unit has been investigated for one year employing measured climatic conditions for representative days of the months. The maximum water production was in September (2.23 m 3 /day) and the least was in January (0.618 m 3 /day). The power consumed by the unit was determined and the mean specific power rate was 0.42 kWh/liter of fresh water. The pilot unit was purchased at a relatively high cost that raises the fixed charges rate, the estimated maximum water cost was 23 $/m 3 for electricity rate of 0.045 $/kWh. A more realistic estimate based on sharing the expenses between the A/C and water production processes reduced the water cost to 13.5 $/m 3 (50.6 Saudi Riyal/m 3 ). The combined A/C- Dehumidifying unit can be efficient for resort areas of high humidity, low water demand and need for air conditioning.