A heat exchange tube for an HVAC system can include at least one reduced diameter section with an integral flattened ridge. The flow of combustion gases through the heat exchanger tubes may be partially constricted inside the reduced diameter sections. When installed in an HVAC system the integral flattened ridges may be angled to intercept the flow of air outside the heat exchanger tubes.

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 heat exchange tube for an HVAC system can include at least one reduced diameter section with an integral flattened ridge. The flow of combustion gases through the heat exchanger tubes may be partially constricted inside the reduced diameter sections. When installed in an HVAC system the integral flattened ridges may be angled to intercept the flow of air outside the heat exchanger tubes.

A heating, ventilation, and air conditioning system includes a heating system. The heating system portion of the HVAC unit can comprise an array of heat exchanger tubes attached to a first side of a heat exchanger panel and a burner assembly attached to a second side of the heat exchanger panel. The burner assembly can comprise one or more tabs to facilitate installation and removal of the burner assembly within the HVAC system. The heat exchanger panel can comprise one or more slots that receive the one or more tabs of the burner assembly.

A system of capturing waste heat includes a heat recovery unit (20) having a heat exchanger (35) arranged to transfer heat between a fluid circulating in a refrigerant loop (60) and a fluid circulating in a solar loop (70) and another heat exchanger (39) arranged to transfer heat between the fluid in the solar loop (70) and a fluid circulating in a water loop (50). Controllable first, second, and third three-way valves (V1-V3) provide or prevent, depending on fluid temperatures, an A-B, B-C, and A-C flow path through the valve. The first valve (V1) is arranged in the water loop (50) upstream of the second heat exchanger (39). The second (V2) is arranged in the solar loop (70) upstream of the second heat exchanger (39). The third valve (V3) is arranged in the solar loop (70) between the first and second heat exchangers (35, 39).

A fluid transportation network (1) comprises a plurality of parallel zones (Z1, Z2), fed by a common supply line (L), with a regulating zone valve (V1, V2) in each zone (Z1, Z2) for regulating a flow of fluid (.sub.1, .sub.2) through the respective zone (Z1, Z2). A processing unit (RE) receives valve positions (pos.sub.1, pos.sub.2) of the regulating zone valves (V1, V2) and determines and sets an adjusted valve position for a line valve (VE) arranged in the supply line (L), depending on the valve positions (pos.sub.1, pos.sub.2) of the regulating zone valves (V1, V2). A processing unit (RE) further receives a measurement of a total flow of fluid (.sub.tot) through the supply line (L) and determines and sets adjusted valve positions for the regulating zone valves (V1, V2), depending on the measurement of the total flow of fluid (.sub.tot) through the supply line (L).

A greenhouse, for cold weather climates, is configured with a gable that is offset toward the north wall and therefore the south extension of the roof, from the gable to the south wall is longer than the north extension. A greater amount of light can enter through this south extension and the inside surface of the north wall is configured with a reflective surface to allow light to be more uniformly distributed around the plants. The north wall may have no widows and may be thermally insulated to prevent the greenhouse from getting too cold during the night. A ground to air heat transfer (GAHT) system may be configured to produce a flow of greenhouse air under the greenhouse for heat transfer, to moderate the temperature of the greenhouse. A thermal medium may flow to a thermal reservoir for heat exchange with the conduits of the GAHT system.

A heat exchanger for an apparatus including a burner has at least one tube extending along a centerline from an inlet end adjacent the burner to an outlet end. A plurality of indentations is formed in the tube adjacent the inlet end and extend radially inward towards the centerline. The indentations are formed in opposing pairs extending towards one another to a depth sufficient to create turbulent fluid flow through the inlet end of the tube.

A thermoelectric battery system includes a heat pump configured to generate heat. A buffer tank is thermally coupled to the heat pump and configured to store the generated heat in boiler water. A thermal battery is thermally coupled to the buffer tank. The thermal battery provides at least one of hot water for domestic use, hydro-heating, or hydro-cooling. The first thermal battery includes: an inner tank configured to contain a portion of boiler water and an outer tank containing a phase change material. The outer tank surrounds the inner tank and is separated therefrom by a thermally conductive wall. The outer tank is configured to supply heat to the inner tank. A heat exchanger disposed in the inner tank is configured to heat potable water flowing therethrough to enable potable water to be heated by boiler water to produce domestic hot water.

A high-efficient central chiller plant system with variable load by phase change material thermal energy storage includes a refrigeration unit and a phase change thermal energy storage. The refrigeration unit operates under the highest COP. If the refrigerating output is higher than the demand of cooling load, the phase change thermal energy storage stores energy by the phase change. Contrarily, if the refrigerating output cannot meet the demand of cooling load, the phase change thermal energy storage releases energy to supply the insufficient cooling load of the refrigeration unit. So that users can set the operation strategy of the refrigeration unit according to the usage statistics, and let the refrigeration unit operate efficiently with the cooperation of the phase change thermal energy storage, thereby effectively improving the energy efficiency of the system operation to save energy. Compared with the existing central chiller system, it saves energy more than 40%-70%.