A method of defrost operation optimization in a heat pump includes launching a heating mode after completion of a performed defrost operation, measuring, after launching the heating mode, a heat transfer capability, determining if the measured heat transfer capability is less than or equal to a predetermined heat transfer capability limit for a non-iced condition, and reinforcing a next defrost operation if the measured heat transfer capability is greater than the predetermined gap limit.

A heat pump system includes a compression device 12, a heat rejecting heat exchanger 14, an expansion device 18 and a heat absorbing heat exchanger 16; wherein the expansion device 18 provides a controllable degree of expansion. The heat pump system is operated in accordance with a method including determining a temperature indicative of frosting conditions on an exterior surface of the heat absorbing heat exchanger 16; operating the heat pump system in a first mode if the temperature indicative of frosting conditions is above a threshold value, and operating the heat pump system in a second mode if the temperature indicative of frosting conditions is within a range of temperatures that is below the threshold value.

A heat pump boiler is disclosed. The heat pump boiler includes a compressor. The heat pump boiler further includes an exterior heat exchanger that is configured to transfer heat between refrigerant and exterior air. The heat pump boiler further includes an interior heat exchanger that is configured to transfer heat between refrigerant and water. The heat pump boiler further includes a channel change valve that is configured to provide refrigerant compressed by the compressor to the exterior heat exchanger or the interior heat exchanger. The heat pump boiler further includes a first boiler heat exchanger that is configured to heat water that has passed through the interior heat exchanger from heat generated through combustion. The heat pump boiler further includes a second boiler heat exchanger that is configured to transfer heat between refrigerant and gas discharged from the first boiler heat exchanger.

A control device controls a heating capacity during a heating operation and a defrosting capacity during a defrosting operation. The defrosting capacity of the first refrigeration cycle unit is determined to fall within a range satisfying a first determination condition and within a range satisfying a second determination condition. The first determination condition is a condition that a sum of a load capacity of a load device when the first defrosting start condition is satisfied, and the defrosting capacity of the first refrigeration cycle unit does not exceed the heating capacity of a second refrigeration cycle unit. The second determination condition is a condition that a sum of an inter-unit defrosting interval and a defrosting period of the first refrigeration cycle unit does not exceed a shortest defrosting interval of the second refrigeration cycle unit.

A heat pump includes a compressor, a metering device, a first heat exchanger, a second heat exchanger, a first fan, a second fan, and a refrigerant circuit between the first heat exchanger and the second heat exchanger. A thermal storage device coupled to the refrigerant circuit is configured to store thermal energy when the refrigerant fluid is above a threshold temperature and discharge thermal energy when the refrigerant fluid is below the threshold temperature. The heat pump is operated in a heating mode in which heat is transferred from the refrigerant fluid at the first heat exchanger and the temperature of the refrigerant fluid at the thermal storage device is above the threshold temperature, and a defrost mode in which heat is transferred to the refrigerant fluid at the first heat exchanger and the temperature of the refrigerant fluid at the thermal storage device is below the threshold temperature.

A refrigeration apparatus includes a heat source-side unit and a utilization-side unit that are connected to each other, and performs a refrigeration cycle in which a high pressure of a refrigerant reaches or exceeds a critical pressure. The refrigeration apparatus also includes a control unit configured to perform a first action of returning the refrigerant to the heat source-side unit when a stop condition of the utilization-side unit is satisfied, and a second action of prohibiting the first action when a pressure at the heat source-side unit is equal to or more than the critical pressure of the refrigerant. This configuration suppresses damage to a refrigerant storage reservoir and the like in returning the refrigerant to the heat source-side unit.

A refrigerating and air-conditioning apparatus performs, even during a heating operation under air conditions leading to formation of frost, a defrosting operation while simultaneously continuing the heating operation and improves comfort through heating by securing an appropriate amount of ventilation. A plurality of refrigeration cycles independently performs a heating operation and a defrosting operation. By controlling a ventilation damper of an indoor unit that is to perform a defrosting operation to increase the amount of ventilation, a prior ventilation operation for securing the time-averaged required amount of ventilation including the period in which the defrosting operation is being performed is performed before the defrosting operation, and after the prior ventilation is terminated, the defrosting operation is started.

A method for determining when to initiate a defrost mode of a heat pump includes monitoring a heating capacity of an evaporator of the heat pump during operation of the heat pump in a heating mode, determining a threshold associated with the heating capacity, and initiating a defrost mode when the heating capacity of the evaporator is less than or equal to the threshold.

A heat exchanger includes a plurality of principal heat exchange sections and auxiliary heat exchange sections. Each of the auxiliary heat exchange sections is in series connection to a corresponding one of the principal heat exchange sections. Of tube number ratios of the number of the flat tubes constituting each of the heat exchange sections to the number of the flat tubes constituting a corresponding one of the auxiliary heat exchange sections, the first principal heat exchange sections which is the lowermost one has the smallest tube number ratio. Consequently, discharge of liquid refrigerant from a lower portion of the first principal heat exchange section is accelerated during defrosting, thereby shortening the time required for defrosting.

Provided is an air-conditioning apparatus including a plurality of indoor units for an outdoor unit, which is capable of determining whether there is occurrence of frost formation on the outdoor unit during a heating operation so as to enable a transition to a defrosting operation at an appropriate timing. Each of the indoor units is configured to transmit an operating-state notification for notifying a self-operating state to the outdoor unit. The outdoor unit is configured to determine the number of indoor units performing the heating operation among the plurality of indoor units based on the operating-state notifications, and determine the occurrence of the frost formation after elapse of a preset time period from a time at which the number of the indoor units performing the heating operation changes.