Ventilator system and method

Abstract

The ventilator system and method use a isolating heat exchanger to selectively transfer heat between exhaust air leaving an enclosed space and outside air entering the enclosed space. The system operates in three basic modes, under the control of a microprocessor-based controller which is responsive to the temperatures inside and outside of the enclosed space. In the heating mode, heat is transferred from the exhaust air to the outside air when the enclosed space requires heating. In the cooling mode, heat is transferred from the outside air to the exhaust air when the outside air temperature is higher than that in the enclosed space. In the supplemental cooling mode, heat transfer between the exhaust and outside air is reduced or eliminated when the outside air temperature is below the desired temperature in the enclosed space and cooling is required. In the heating mode, the heat exchanger is selectively heated when necessary to defrost it. A by-pass is provided for the introduction of outside air in order to avoid heating of the outside air by the exhaust air during the supplemental cooling mode of operation, and/or provide fresh air to the enclosed space without cooling the heat exchanger while it is being defrosted.

What is claimed is:  
     
         1 . A method of ventilating an enclosed space using an air handling system including an isolating heat exchanger for conducting exhaust air from said enclosed space and outside air into said enclosed space and exchanging heat between said exhaust air and said outside air while isolating the flows of said outside and exhaust air from one another, an enclosed space air temperature sensor, an outside air temperature sensor, a first fan to move said exhaust air through said heat exchanger, a second fan to move said outside air through said heat exchanger, and a programmed controller for controlling the flow of said exhaust air and said outside air and the heat transfer therebetween, said method comprising: 
 (a) during a first cooling mode, causing heat to be transferred from said outside air to said exhaust air when the outside air temperature is greater than a desired enclosed space temperature;    (b) during a second cooling mode, reducing or eliminating the transfer of heat from said exhaust air to said outside air through said heat exchanger when said outside air temperature is lower than said desired enclosed space temperature, and said space temperature is greater than said desired space temperature.    
     
     
         2 . A method as in  claim 1  including the step of, during a first heating mode, utilizing said controller in causing heat to be transferred from said exhaust air to said outside air when said outside air temperature is at a temperature which is below said desired space temperature by at least a pre-determined amount.  
     
     
         3 . A method as in  claim 2  in which said air handling system includes a sensor for detecting freezing conditions in said heat exchanger, and including the step of utilizing said controller in causing the heating of said heat exchanger to alleviate said freezing condition.  
     
     
         4 . A method as in  claim 3  in which the heat exchanger heating step includes reducing the flow of sub-freezing outside air through said heat exchanger.  
     
     
         5 . A method as in  claim 3  in which the heat exchanger heating step includes re-circulating said exhaust air through said heat exchanger in the path otherwise taken by said outside air.  
     
     
         6 . A method as in  claim 3  in which the heat exchanger heating step includes one or more steps selected from the group consisting of; reducing the flow of outside air through said heat exchanger while maintaining the flow of exhaust air therethrough; recirculating said exhaust air through said heat exchanger; and applying heat from a heat source to said heat exchanger.  
     
     
         7 . A method as in  claim 1  including the step of using evaporative cooling during said first cooling mode to cool said exhaust air prior to its entering said heat exchanger.  
     
     
         8 . A method as in  claim 7  in which said evaporative cooling comprises one or more steps selected from the group consisting of; spraying water into said exhaust air; wetting a membrane with water and contacting said exhaust air with said membrane; and spraying water into said exhaust air and onto a membrane contacting said exhaust air.  
     
     
         9 . A method as in  claim 1  in which said air handling system includes a by-pass duct and fan for selectively introducing outside air into said enclosed space without flowing through said heat exchanger; and including the step of operating the by-pass fan to introduce outside air into said space during said second cooling mode.  
     
     
         10 . A method as in  claim 9  including the step of operating said by-pass fan during defrosting of said heat exchanger.  
     
     
         11 . A method as in  claim 1  in which the step of substantially eliminating the transfer of heat during said second cooling mode is performed by reducing or eliminating the flow of exhaust air through said heat exchanger while flowing said outside air therethrough.  
     
     
         12 . A method of ventilating an enclosed space using an air handling system including an isolating heat exchanger for conducting exhaust air from said enclosed space and outside air into said enclosed space and exchanging heat between said exhaust air and said outside air while isolating the flows of said outside and exhaust air from one another, an enclosed space air temperature sensor, an outside air temperature sensor, a first fan to move said exhaust air through said heat exchanger, a second fan to move said outside air through said heat exchanger, and a programmed controller for controlling the flow of said exhaust air and said outside air and the heat transfer therebetween, said method comprising: 
 during a heating mode, causing heat to be transferred from said exhaust air to said outside air when said outside air temperature is at a first temperature which is below a desired space temperature by at least a pre-determined amount, and    during a cooling mode, reducing or eliminating the transfer of heat from said exhaust air to said outside air through said heat exchanger when said outside air temperature is above said first temperature but below said desired temperature, and said space temperature is greater than said desired space temperature.    
     
     
         13 . A method of ventilating an enclosed space using an air handling system including an isolating heat exchanger for conducting exhaust air from said enclosed space and outside air into said enclosed space and exchanging heat between said exhaust air and said outside air while isolating the flows of said outside and exhaust air from one another, an enclosed space air temperature sensor, an outside air temperature sensor, a first fan to move said exhaust air through said heat exchanger, a second fan to move said outside air through said heat exchanger, and a programmed controller for controlling the flow of said exhaust air and said outside air and the heat transfer therebetween, said method comprising: cooling said enclosed space by substantially eliminating the transfer of heat from said exhaust air to said outside air through said heat exchanger when said outside air temperature is below a desired space temperature but above a temperature at which heating of the enclosed space is required, and said space temperature is greater than said desired space temperature.  
     
     
         14 . A method as in  claim 13  in which the transfer of heat from said exhaust air is reduced or eliminated by one of more of the steps consisting of: by-passing outside air around said heat-exchanger; and reducing or eliminating the flow of exhaust air through said heat exchanger  
     
     
         15 . A system for ventilating an enclosed space, said system including an outside air duct, an inside air duct, an inside air temperature sensor, an outside temperature sensor, a heat exchanger with two sets of isolated air flow passages, one of which communicates with said outside air duct, and the other of which communicates with said inside air duct, an inside air fan positioned to force inside air through said inside air duct and said heat exchanger, an outside air fan positioned to force said outside air through said outside air duct and said heat exchanger, and a control circuit including a programmed processor for selectively operating said air fans and the exchange of heat between said inside air and said outside air in response to temperature signals received from said temperature sensors.  
     
     
         16 . A system as in  claim 15  including an evaporative cooler for selectively cooling said inside air before it passes through said heat exchanger.  
     
     
         17 . A system as in  claim 15  in which said evaporative cooler includes a membrane in the flow path of said inside air and a water sprayer to supply water to wet said membrane.  
     
     
         18 . A system as in  claim 15  including a sensor for sensing freezing conditions in said heat exchanger, said processor being programmed to cause said heat exchanger to be heated when the freezing conditions are detected.  
     
     
         19 . A system as in  claim 18  in which said processor is programmed to cause said heat exchanger to be heated by reducing the flow of outside air through said heat exchanger while maintaining the flow of inside air therethrough.  
     
     
         20 . A system as in  claim 15  including a by-pass conduit and a fan for introducing outside air into said enclosed space without passing said outside air through said heat exchanger, said processor being programmed to cause outside air to flow through said by-pass in response to signals indicating that the outside air temperature is below a desired air temperature in said space and above a temperature at which heating in said space is needed.  
     
     
         21 . A system as in  claim 15  in which said processor is programmed to cause heat to be transferred from said inside air to said outside air in said heat exchanger when said inside air temperature sensor indicates that heating is needed in said enclosed space, to cause heat to be transferred from said inside air to said outside air when said inside air temperature sensor indicates that cooling is needed in said enclosed space and said outside air temperature sensor indicates that said outside air temperature is higher than the inside air temperature, and to cause no heat to be transferred between said inside air and outside air when cooling in said space is needed and said outside air temperature is below said inside air temperature.  
     
     
         22 . A system as in  claim 15  in which said heat exchanger is made of crossed plastic conduits assembled together.  
     
     
         23 . A system as in  claim 20  in which said by-pass conduit has an outlet into said outside air duct, and including gravity louvers normally covering said outlet of said by-pass conduit, said louvers being opened by air pressure from said by-pass fan.  
     
     
         24 . A system as in  claim 18  in which said inside and outside ducts have inlet sections, and including louvers at the inlet sections and another louver between said sections, said louvers being selectively operable to recirculate inside air through said heat exchanger and reduce or eliminate outside air flow in response to the detection of freezing conditions in aid heat exchanger.