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In fluid dynamics, the entrance length is the distance a flow travels after entering a pipe before the flow becomes fully developed. [1] Entrance length refers to the length of the entry region, the area following the pipe entrance where effects originating from the interior wall of the pipe propagate into the flow as an expanding boundary layer.
The annual performance factor of heat pumps is also relatively high, especially compared to air-sourced heat pumps. A study of 40 systems commissioned up to 2018 showed that the heat pumps achieved an seasonal COP of at least 4 for the majority of the systems studied; the highest seasonal COP values were about 6. [1]
Specifically, the heat pump transfers thermal energy using a heat pump and refrigeration cycle, cooling the cool space and warming the warm space. [1] In winter a heat pump can move heat from the cool outdoors to warm a house; the pump may also be designed to move heat from the house to the warmer outdoors in summer.
The thermal boundary layer thickness, , is the distance across a boundary layer from the wall to a point where the flow temperature has essentially reached the 'free stream' temperature, . This distance is defined normal to the wall in the y {\displaystyle y} -direction.
Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump, air conditioning and refrigeration systems. [1] A heat pump is a mechanical system that transmits heat from one location (the "source") at a certain temperature to another location (the "sink" or "heat sink") at a higher temperature. [2]
Central heating systems: These systems produce heat in one central location and distribute it throughout the building. This category includes furnaces, boilers, and heat pumps. [1] [2] Distributed heating systems: These systems generate heat in the space they are to heat, without extensive duct systems. Examples include electric space heaters ...
An air source heat pump can be used to air condition the building during hot weather, and to warm the building using heat extracted from outdoor air in cold weather. Air-source heat pumps are generally uneconomic for outdoor temperatures much below freezing. In colder climates, geothermal heat pumps can be used to extract heat from the ground ...
A heat pump in combination with heat and cold storage. A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that use a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through the seasons.