A thermal storage and exchange heating apparatus includes: a thermal storage tank that stores a heated heat medium; a circulation channel connected to high and low temperature sides of the thermal storage tank, and through which the heat medium circulates; a heat exchanger provided to the circulation channel and configured to exchange heat between the heat medium and a heating object, to heat the heating object; a circulation direction switch configured to switch circulation of the heat medium in the circulation channel between a forward direction from the high-temperature side to the low-temperature side and a reversed backward direction; and a controller configured to cause the heat medium to circulate in the forward direction by switching the circulation direction switch in a heating operation and causing the heat medium to circulate in the backward direction by switching the circulation direction switch after a stop of the heating operation.

The present disclosure relates to a method and a system for preventing freezing when a four-way valve in a heat pump water heater is failed, which includes following acts: In act S1, it is judged that whether current water temperature T is lower than a preset minimum temperature T.sub.min , for the water tank, if yes, perform act S2; if no, perform act S1 again. In act S2, it is judged that whether a cooling rate Td of the current water temperature T is greater than or equal to a preset rate ΔT; or, it is judged that whether the current water temperature T satisfies T<T.sub.min−a and whether T<T.sub.min−a stands for a first time period t1, in which a is a limit value of a temperature difference; if at least one yes, perform act S3, otherwise, return to act S1. In act S3, a heat pump system is controlled to stop and an electric auxiliary heating system is started. By judging whether a cooling rate Td of the current water temperature T is greater than or equal to a preset rate ΔT; or by judging whether the current water temperature T satisfies T<T.sub.min−a and whether T<T.sub.min−a stands for a first time period t1, it may be judged precisely that whether the four-way valve is failed, which avoids a misjudgment.

Feedwater to be supplied to a feedwater tank via a feedwater path is passed through a waste heat recovery heat exchanger, a supercooler, and a condenser in sequence. A heat source fluid such as heat source water is passed through an evaporator and the waste heat recovery heat exchanger in sequence. The waste heat recovery heat exchanger is an indirect heat exchanger between the feedwater supplied to the feedwater tank via the feedwater path and the heat source fluid having passed through the evaporator. The supercooler is an indirect heat exchanger between the feedwater supplied to the feedwater tank via the feedwater path and a refrigerant supplied from the condenser to an expansion valve.

A controller performs a first operation in which a heat source device directly or indirectly heats water in a first channel of a heat exchanger and a second operation in which the heat source device directly or indirectly cools the water in the first channel of the heat exchanger after the first operation ends.

A heat storage system includes a compressor that compresses refrigerant; a heat storage tank that stores a heating medium; heat exchange means provided outside the heat storage tank for heating the heating medium using heat of the refrigerant compressed by the compressor; a heat accumulating circuit including a feed path that feeds the heating medium flowing out of the heat storage tank to the heat exchange means, a return path that returns the heating medium heated by the heat exchange means into the heat storage tank, and a pump that circulates the heating medium; and control means capable of executing an initial operation that controls an operating frequency of the compressor at the beginning of a heat accumulating operation in which the heating medium heated by the heat exchange means is accumulated in the heat storage tank. The initial operation includes a first operation that maintains the operating frequency at a first frequency and, after the first operation, a second operation that maintains the operating frequency at a second frequency higher than the first frequency.

The invention relates to a method for operating a circulation system (10) comprising a heating device having an inlet port and an outlet port for controlling the temperature of water, and comprising a pipe system having a plurality of strings which include one or more sections of a given thermal coupling to the surroundings and are connected by means of nodes, one or more of the pipes of the pipe system being designed as a supply pipe (4, 5, 6), at least one individual delivery pipe (7) connected to a removal point (9) and at least one pipe designed as a circulation pipe (10a) being connected to the supply pipe(s) (4, 5, 6), said method comprising the steps: —setting a water temperature at the outlet port to a value Ta by means of the heating device; —setting a volumetric flow rate at the inlet port to a value Vz, and comprising the following steps: —determining, in particular calculating, a temperature change of the water between the start region and the end region according to a model of the axial temperature change for the first section connected to the outlet port, starting from a temperature start value TMA* and a volumetric flow rate start value Vz*; —determining, in particular calculating, a temperature change of the water between the start region and the end region for each further given section according to the model of the temperature change, subject to the boundary condition that the water temperature in the start region of the given section is the same as the water temperature in the end region of the section to which the given section is connected; and —selecting the value Ta of the water temperature and the value Vz of the volumetric flow rate at the outlet port in such a way that in the end region of each section the water temperature TME is in a specified temperature range around Tsoll, in particular at the inlet port (12a, 14b) the water temperature Tb<Tsoll is set with Tsoll−Tb<Θ, where Θ>0 is a specified value. Furthermore, the invention also relates to a circulation system for carrying out the method.

A hot-water supply system heats up water by power generated by power generation means. The hot water supply system includes a compressor and a water heat-up unit. In the hot-water supply system, the compressor compresses refrigerant and circulates the refrigerant through a refrigerant circuit. The water heat-up unit heats up water by changing, in accordance with the generated power, a rotation rate of an electric motor for driving the compressor.

A hot water unit fluid supply control system for a hot water unit is disclosed. The hot water unit has a heating system that is operable in a heating cycle to heat up water in at least a first region of the water unit, and a sensor arrangement for sensing a temperature of water of the hot water unit. The control system comprises a control unit configured to: receive operational data relating to an operation of the heating system; receive temperature data from the sensor arrangement; and allow for a volume of water from the first region to be released from the hot water unit as treated water or usable water based on: the operational data, and the temperature data from the sensor arrangement.

A hot water supply system includes a first heat pump, a second heat pump, and a hot water storage tank. The first heat pump heats water stored in the hot water storage tank to make hot water. The second heat pump heats water supplied to the hot water storage tank.

The disclosed technology includes systems and methods for operating a fluid heating device comprising a heat pump and an electric heating element. The disclosed technology can include a system and method that can receive current data from a current sensor and temperature data from a temperature sensor, determine whether the current is greater than or equal to a threshold current and whether the temperature is greater than or equal to a threshold temperature, and output a control signal to heat the fluid using the heat pump only or the electric heating element only based on the current data and the temperature data.