Method for reducing vapor generation in a temperature controlled liquid holding tank

A method for reducing vapor generation in a temperature controlled fuel tank in a motor vehicle using an apparatus having hot and cold fluid sources, a heat exchanger having hot and cold valves and an air blower to force temperature conditioned discharge air flow onto the fuel tank, comprising the steps of:

• producing a signal representing an operating mode, said signal having a first state when indicating a first mode of operation and a second state when indicating a second mode of operation;
• sensing a fuel temperature in the fuel tank and generating an actual fuel temperature signal;
• producing a signal representing a desired fuel temperature;
• comparing said actual and desired fuel temperature signals and producing a first error signal from said comparison;
• producing a gain signal in response to said operating mode signal and said error signal;
• producing a desired discharge air temperature signal in response to said gain signal and said first error signal representing the difference between said desired fuel temperature and said actual fuel temperature;
• sensing a discharge air temperature in said discharge air flow and generating an actual discharge air temperature signal;
• comparing said actual and desired discharge air temperature signals and producing an second error signal from said comparison;
• producing a first control signal in response to said second error signal representing the difference between said desired discharge air temperature and said actual discharge air temperature for producing a first control signal;
• and
• actuating the heat exchanger by supplying said first control signal to the cold and hot valves.