A constant temperature and humidity air conditioning system with direct expansion temperature and humidity independent control air handling units

 To avoid the reheat energy penalty of a conventional constant temperature and humidity air conditioning system, a novel constant temperature and humidity control air conditioning system is developed. This system is comprised of three stage direct expansion air cooled sections, a heater, a humidifier, along with an advanced control strategy, to achieve decoupling the temperature control with the humidity control. This air conditioning system also has the advantage of simple configuration and flexible arrangement without the expense of too much cost. A simulation of an actual project in Tianjin is conducted to evaluate the energy performance of the system using IES-VE 2018. Three systems are simulated, a conventional constant temperature and humidity system as a baseline for comparison purpose, a constant air volume and a variable air volume configuration for the novel system. Simulation results show that the temperature and humidity of zone are well controlled in required range and the novel air conditioning system can achieve 15% energy saving under constant air volume working condition, 35% energy saving under variable air volume working condition compared with the conventional system. But the thermal zone is more volatile when the novel air conditioning system under variable air volume working condition(VAV system).So the VAV system is more suitable for the thermal zone where the accuracy of temperature and humidity control is not strict.