A heat exchanger tube includes a first pass for at least partially combusting a fuel and the first pass having a modified shape including a minor diameter and major diameter that reduces the external pressure drop of an external fluid flowing across the heat exchanger tube. A HVACR system includes a heat exchanger tube with a first heat exchange pass that at least partially combusts a fuel and has a modified shape. A method of making a heat exchanger including configuring a first heat exchange pass such that the major diameter of modified portion of the first heat exchange pass is oriented towards an incoming direction of the process fluid.

A piping system for recovery heat energy from an exhaust gas in a heat recovery furnace, the piping system comprising a piping inlet, where the piping inlet transects a wall of a stack zone of the heat recovery furnace, a piping run, the piping run fluidly connected to the piping inlet, and a piping outlet, the piping outlet fluidly connected to the piping run, where the piping outlet transects the wall of the stack zone of the heat recovery furnace, where the piping system is positioned in a stack zone of the heat recovery furnace between a stack inlet and a stack outlet.

An air conditioning system includes a heat pump unit including a radiator usable with a refrigerant, a gas furnace unit including a heating section arranged to heat passing air, a blower arranged to generate an air flow that passes through the radiator and the heating section, a first temperature sensor provided in a room, and a controller configured to control each action of the heat pump unit, the gas furnace unit, and the blower. The temperature sensor detects an indoor temperature in the room. The controller causes the gas furnace unit to operate as a heat source unit when a difference value obtained by subtracting the indoor temperature from a set temperature is equal to or greater than a first threshold at startup, and causes the heat pump unit to operate as a heat source unit when the difference value is less than the first threshold at startup.

The present disclosure discloses a defrosting control method, a central controller and a heating system. The defrosting control method comprises: heating fluid in a flow passage between an inlet and an outlet of a first heat source by a second heat source, at least in a part of process of defrosting by the first heat source; acquiring an operation parameter of the first heat source, wherein the operation parameter comprises a water outlet temperature and/or a water return temperature and/or an operation parameter of a compressor of the first heat source, comparing a current value of the acquired operation parameter with a preset range of the operation parameter, and adjusting a heat exchange amount between the second heat source and the fluid when the acquired current value is within the preset range. The defrosting control method, the central controller and the heating system provided by the present disclosure can improve the defrosting efficiency while considering the heating comfort, and ensure the stable operation of the defrosting process.

A system for simultaneous heat recovery and flue gas cleaning, comprising at least one heat pump (300), at least one combined heat recovery and flue gas cleaning unit (1) comprising a heat exchanger (10), said unit having an inlet (20) directing a flow of flue gas into said unit, an outlet (40) for allowing said flow of flue gas to leave said unit, wherein said heat pump is adapted to deliver a flow of cooling media to the heat exchanger at a temperature in the interval of about 4 to about +4 C. This system is compact, efficient and easy to operate. The system can easily be expanded thanks to a modular concept, and it is well suited for mobile applications. A method for heat recovery and flue gas cleaning is also disclosed.

An air conditioning system includes a heat pump having a refrigerant radiator, a gas furnace unit having a heating section to heat passing air, a blower generating air flow through the radiator and the heating section, and a controller controlling operation of the heat pump unit, the gas furnace unit, and the blower. The controller has a first operating mode in which the gas furnace unit operates alone as a heat source unit, a second operating mode in which the heat pump unit operates alone as a heat source unit, and a third operating mode in which the gas furnace unit and the heat pump unit operate at the same time as a heat source unit. The controller is configured to select the operating modes based on a parameter relating to outside air temperature that is the temperature of outside air.

A heating control device including input/output ports, a memory operable to store smoke output thresholds, and a microprocessor. The microprocessor is configured to transmit a first electrical signal to operate an air circulation fan at a first speed and a heating unit in a first configuration to burn a lubricant at a first temperature where less than all of the burners are active. The microprocessor is further configured to obtain a smoke output measurement for the first temperature, compare the smoke output measurement to the smoke output threshold, and transmit a second electrical signal to transition the air circulation fan to a second speed to burn the lubricant at a second temperature that is greater than the first temperature when the smoke output measurement is less than the smoke output threshold and is less than the first temperature when the smoke output measurement is greater than the smoke output threshold.

A heating system comprising an air circulation fan, a heating unit, a memory that is operable to store a temperature map, and a microprocessor. The microprocessor is configured to operate the air circulation fan at a first speed and the heating unit in a first configuration. When the heating unit is in the first configuration, the heating unit is configured to achieve a first temperature and such that less than all of the burners are active. The microprocessor is also configured to receive a temperature set point and to determine a second speed for the air circulation fan using the temperature set point and the temperature map in response to receiving the temperature set point. Further, the microprocessor is configured to transition the air circulation fan from the first speed to the second speed in response to determining the second speed.

An air handling apparatus for a HVAC system of a building. The air handling apparatus includes an enclosure having at least one inlet opening for drawing outside air into the enclosure, and at least one outlet opening for directing air from within the enclosure to outside the enclosure. At least one fan is mounted within the enclosure for drawing air through the enclosure. A burner box is centrally located within the enclosure for heating outside air drawn into the enclosure through the at least one inlet opening.

A heating control system including an air circulation fan, a heating unit, a memory, and a microprocessor. The microprocessor is configured to operate the air circulation fan at a first speed and the heating unit in a first configuration where less than all of the burners are active. The microprocessor is further configured to determine a first temperature difference, compare the first temperature difference to a first temperature difference threshold, and transition the air circulation fan from the first speed to a second speed when the first temperature difference is less than the first temperature difference threshold. The microprocessor is further configured to determine a second temperature difference, compare the second temperature difference to a second temperature difference threshold, and transition the air circulation fan from the second speed to a third speed when the second temperature difference is less than the second temperature difference threshold.