Energy efficient dryer systems

Abstract

A dryer including a housing, a drying chamber disposed within the housing, and a heating element coupled to the housing. The dryer further includes an intake configured to supply intake air to the drying chamber and an exhaust vent configured to vent exhaust air out of the drying chamber. The intake, the drying chamber, and the exhaust vent define an air flow path from the intake through the drying chamber and out the exhaust vent. The dryer includes a heat exchanger and a heat pump having a condenser. The heat exchanger and the heat pump are each configured to absorb thermal energy from the exhaust air and transfer the thermal energy to the intake air. The air flow path is configured such that the intake air is heated directly or indirectly by the heat exchanger prior to the intake air being further heated directly or indirectly by the condenser. The air flow path is configured such that the intake air is further heated directly or indirectly by the condenser prior to the intake air entering the drying chamber.

What is claimed: 
     
         1 . A dryer comprising:
 a housing;   a drying chamber disposed within the housing;   a heating element coupled to the housing;   an intake configured to supply intake air to the drying chamber;   an exhaust vent configured to vent exhaust air out of the drying chamber;   a heat exchanger; and   a heat pump having a condenser coupled to the drying chamber;   wherein the intake, the drying chamber and the exhaust vent define an air flow path from the intake through the drying chamber and out the exhaust vent;   wherein the heat exchanger and the heat pump are each configured to absorb thermal energy from the exhaust air;   wherein the air flow path is configured such that the intake air is heated directly or indirectly by the heat exchanger prior to the intake air entering the drying chamber; and   wherein the condenser is configured to provide heat to the drying chamber.   
     
     
         2 . The dryer of  claim 1  wherein the heat pump includes an evaporator. 
     
     
         3 . The dryer of  claim 2  wherein the air flow path is configured such that the exhaust air leaving the drying chamber is cooled directly or indirectly by the evaporator prior to the exhaust air transferring thermal energy to the heat exchanger. 
     
     
         4 . The dryer of  claim 3  wherein the air flow path is configured such that the exhaust air is further cooled directly or indirectly by the heat prior to exiting the exhaust vent. 
     
     
         5 . The dryer of  claim 1  wherein the condenser is further configured to provide heat to the intake air prior to the intake air entering the drying chamber. 
     
     
         6 . The dryer of  claim 5 , wherein the air flow path is configured such that the intake air is at least partially heated directly or indirectly by the heat exchanger prior to receiving the heat from the condenser. 
     
     
         7 . The dryer of  claim 1 , wherein the air flow path is configured to pass the intake air over the heating element after the intake air has been heated directly or indirectly by the heat exchanger. 
     
     
         8 . The dryer of  claim 1  further comprising a controller configured to receive a user input corresponding to a mode of operation for the dryer, wherein the controller is configured to adjust the heating element and adjust an operating parameter of the heat pump in response to the user input. 
     
     
         9 . The dryer of  claim 8  further comprising a sensor configured to provide a feedback signal indicative of an air temperature to the controller. 
     
     
         10 . The dryer of  claim 9  wherein the controller is configured to adjust the heating element in response to the feedback signal indicative of the air temperature. 
     
     
         11 . The dryer of  claim 9  wherein the heat pump includes an evaporator and a compressor; wherein the operating parameter of the heat pump is a compressor pressure; and
 wherein the controller adjusts the compressor pressure in response to the feedback signal indicative of the air temperature. 
 
     
     
         12 . The dryer of  claim 8  wherein the heat pump includes an evaporator and a compressor; wherein the operating parameter of the heat pump is a compressor pressure; and wherein the controller adjusts the compressor pressure in response to a feedback signal indicative of an air humidity. 
     
     
         13 . A dryer, comprising:
 a housing;   a drying chamber disposed within the housing;   a heating element coupled to the housing;   an intake configured to supply intake air to the drying chamber;   an exhaust vent configured to vent exhaust air out of the drying chamber;   a heat exchanger; and   a heat pump having an evaporator;   wherein the intake, the drying chamber, and the exhaust vent define an air flow path from the intake through the drying chamber and out the exhaust vent;   wherein the heat exchanger and the heat pump are each configured to absorb thermal energy from the exhaust air and transfer the thermal energy to the intake air;   wherein the air flow path is configured such that the exhaust air leaving the drying chamber is cooled directly or indirectly by the evaporator prior to the exhaust air being further cooled directly or indirectly by the heat exchanger; and   wherein the air flow path is configured such that the exhaust air is cooled directly or indirectly by the heat exchanger prior to the exhaust air exiting the exhaust vent.   
     
     
         14 . The dryer of  claim 13  wherein the heat pump includes a condenser. 
     
     
         15 . The dryer of  claim 14  wherein the air flow path is configured such that the intake air is heated directly or indirectly by the condenser after the intake air receives thermal energy from the heat exchanger. 
     
     
         16 . The dryer of  claim 15  wherein the air flow path is configured such that the intake air is heated directly or indirectly by the heat exchanger prior to receiving thermal energy from the condenser. 
     
     
         17 . The dryer of  claim 15  wherein the intake air is at least partially heated directly or indirectly by condenser while still being heated directly or indirectly by the heat exchanger. 
     
     
         18 . The dryer of  claim 13  wherein the exhaust air is at least partially cooled directly or indirectly by the heat exchanger while still being cooled directly or indirectly by the evaporator. 
     
     
         19 . The dryer of  claim 13 , wherein the air flow path is configured to pass the intake air over the heating element after the intake air has been heated directly or indirectly by the heat exchanger. 
     
     
         20 . The dryer of  claim 13  wherein the heat exchanger is a counter-flow heat exchanger. 
     
     
         21 . The dryer of  claim 13  wherein the heat exchanger is a cross-flow heat exchanger. 
     
     
         22 . The dryer of  claim 13  wherein the heat exchanger is a tubular heat exchanger. 
     
     
         23 . The dryer of  claim 13  wherein the heat exchanger comprises a heat-pipe. 
     
     
         24 . A dryer comprising:
 a housing;   a drying chamber disposed in the housing;   a heating element coupled to the housing;   an intake configured to supply intake air to the drying chamber;   an exhaust configured to direct exhaust air out of the drying chamber;   a heat exchanger; and   a heat pump in thermal communication with the drying chamber;   wherein the intake, the drying chamber and the exhaust define an air flow path from the intake through the drying chamber and out the exhaust;   wherein the heat exchanger and the heat pump are each configured to absorb thermal energy from the exhaust air; and   wherein the air flow path is configured such that the intake air is heated directly or indirectly by the heat exchanger prior to the intake air entering the drying chamber.