Transport refrigeration system utilizing engine waste heat

A transport refrigeration system for controlling a temperature associated with a mobile refrigerated cargo box comprising:

• a refrigeration unit having a refrigerant circuit through which a refrigerant is circulated in heat exchange relationship with air drawn from the mobile refrigerated cargo box;
• a fuel-fired engine for powering the refrigeration unit, the fuel-fired engine having an exhaust system through which exhaust gases generated by the fuel-fired engine are discharged;
• an engine coolant circuit;
• an engine exhaust gases to engine coolant heat exchanger;
• an engine coolant circuit to refrigeration unit heat exchanger;
• wherein the engine exhaust gases to engine coolant heat exchanger comprises a first heat exchanger having a first engine coolant pass interdisposed in the engine coolant circuit and a gas-side pass, the first engine coolant pass disposed in the gas-side pass for passing engine coolant in heat exchange relationship with a flow of engine exhaust gases passing through the gas-side pass, whereby the first engine coolant absorbs heat from the engine exhaust gases and the engine exhaust gases are cooled;
• an engine coolant radiator wherein engine coolant passes in heat exchange relationship with ambient air;
• an engine coolant distribution valve having an inlet port, a first outlet port and a second outlet port, the engine coolant distribution valve disposed in the engine coolant circuit with the inlet port receiving the engine coolant and with the first outlet port in flow communication with a second engine coolant pass of the radiator and the second outlet in flow communication with a third engine coolant pass of the engine coolant circuit to refrigeration unit heat exchanger;
• a controller for selectively positioning the engine coolant distribution valve in one of a first position wherein the inlet port is in flow communication with the first outlet port only and a second position wherein the inlet port is in flow communication with the second outlet port only;
• wherein the controller is configured to position the engine coolant distribution valve in the second position when the refrigeration unit is in a defrost mode for melting frost off an evaporator heat exchanger.