Low temperature cooling and dehumidification device with reversing airflow defrost for dehumidification and water generation applications where cooling coil inlet air is above freezing

A low temperature cooling and dehumidification system comprising:

• a containment enclosing a cooling coil array comprising a coil through which flows a coolant and an air-to-air heat exchanger located above said array;
• an air flow system for directing incoming air through said heat exchanger in a first pass, through said array in which cooling of said air occurs and then through said heat exchanger in a second pass for heat exchange between the two passes of air therethrough, whereby condensate is formed and collects in a bottom of said containment;
• whereby air flow continues during defrosting;
• and
• whereby cooling coil airflow is reversed, and the coldest section of the cooling coil becomes the warmest, thereby promoting defrost, while also keeping the energy, given up by melting frost, in the airstream, thereby providing an energy efficient means for defrosting while not interrupting operation;
• and
• means for removal of frost formation on said coil in the cooling coil array by reversing direction of air flow through said array without interrupting cooling and dehumidification or changing direction of flow into and out of said containment.

A method of limiting frost formation in a low temperature cooling and dehumidification system comprising the steps of:

• passing ambient air through a cooling coil array comprising a coil through which flows a coolant for cooling and dehumidifying said ambient air whereby a condensate is formed on an outside surface of said coil, said condensate freezing to form a frost formation on a coldest portion of said coil;
• periodically removing the frost formation on said coil by reversing direction of air flow through said array, said reversal of air flow recurring without interrupting cooling and dehumidification or changing direction of flow into and out of said cooling and dehumidification system;
• whereby air flow continues during defrosting;
• and
• whereby cooling coil airflow is reversed, and the coldest section of the cooling coil becomes the warmest, thereby promoting defrost, while also keeping the energy, given up by melting frost, in the airstream, thereby providing an energy efficient means for defrosting while not interrupting operation;
• and
• collecting generated condensate in a plenum under said array.

A method of limiting frost formation in a low temperature cooling and dehumidification system comprising the steps of:

• passing ambient air through a containment in which there is a cooling coil array comprising a coil through which flows a coolant for cooling and dehumidifying said ambient air whereby a condensate is formed on an outside surface of said coil, said condensate freezing to form a frost formation on a coldest portion of said coil;
• said ambient air making a first pass through an air-to-air heat exchanger located within said containment located above said coil array and a second pass through said heat exchanger after leaving said coil array;
• periodically removing the frost formation on said coil by reversing direction of air flow through said containment, said reversal of air flow recurring without interrupting cooling and dehumidification or changing direction of flow into and out of said containment;
• whereby air flow continues during defrosting;
• and
• whereby cooling coil airflow is reversed, and the coldest section of the cooling coil becomes the warmest, thereby promoting defrost, while also keeping the energy, given up by melting frost, in the airstream, thereby providing an energy efficient means for defrosting while not interrupting operation;
• and
• collecting generated condensate in a plenum under said array within said containment.