Ultrasonic energy transfer sensing system

A system for determining the energy transfer across a heat exchanger mounted in a duct of an air conditioning system, said heat exchanger having an upstream side and a downstream side such that said heat exchanger transfers energy to air moving through said air conditioning duct, said system measuring the energy transferred to said air by said heat exchanger, said system comprising:

• ultrasonic transmitter means for transmitting ultrasonic waves across said duct on said upstream and downstream sides of said heat exchanger;
• ultrasonic receiver means for receiving said ultrasonic waves on said upstream and downstream sides of said heat exchanger, said receiver means connected to said ultrasonic transmitter means and providing signals indicative of the temperatures of said air upstream and downstream of said heat exchanger and the velocity of air flow through said duct;
• processing means connected to said ultrasonic transmitter means and to said ultrasonic receiver means for determining energy transfer between said heat exchanger and said air based upon said signals indicative of said temperature difference and said velocity;
• wherein said ultrasonic transmitter means comprises a first transmitter transducer located upstream of said heat exchanger and a second transmitter transducer located downstream of said heat exchanger;
• and
• wherein said ultrasonic receiver means comprises a first receiver transducer located upstream of said heat exchanger and oriented with said first transmitter transducer such that a line between said first transmitter transducer and said first receiver transducer is substantially perpendicular to air flowing through said duct, a second receiver transducer located downstream of said heat exchanger such that a line through said second transmitter transducer and said second receiver transducer is substantially perpendicular to the air flowing through said duct, and a third receiver transducer located such that a line between said third receiver transducer and one of said first and second transmitter transducers is at an angle to said air flowing through said duct.