Multi-stage liquid desiccant dehumidification systems and methods

A heating, ventilation, and air conditioning (HVAC) system comprising:

• a refrigerant sub-system operable to circulate a refrigerant between an evaporator and a condenser;
• and
• an air treatment sub-system comprising:
• a three-way heat exchanger operable to transfer heat and moisture between air, a liquid desiccant, and a heat transfer fluid;
• and
• a heat transfer fluid loop for circulating the heat transfer fluid between the three-way heat exchanger and the evaporator for transferring heat between the heat transfer fluid and the refrigerant;
• and
• a pre-treatment heat exchanger operable to transfer heat between the air and one of the refrigerant and the heat transfer fluid upstream from the three-way heat exchanger.

A method of operating an air treatment system, the method comprising:

• channeling a liquid desiccant and a heat transfer fluid to a three-way heat exchanger;
• pre-treating an inlet air stream using a pre-treatment heat exchanger upstream from the three-way heat exchanger to lower at least one of a temperature and a humidity of the inlet air stream, wherein pre-treating the inlet air stream comprises transferring heat from the inlet air stream to the heat transfer fluid upstream from the three-way heat exchanger;
• and
• channeling the pre-treated air stream to the three-way heat exchanger for transferring heat and moisture between the liquid desiccant, the heat transfer fluid, and the pre-treated air stream, producing a treated air stream.