![]() ![]() A thermosiphon is "simpler" than a heat pipe. The wick allows heat pipes to transfer heat when there is no gravity, which is useful in space. A wick is not needed in a thermosiphon because gravity moves the liquid. Heat pipes usually have a wick to return the condensate to the evaporator via capillary action. The thermosiphon has been sometimes incorrectly described as a 'gravity return heat pipe'. If the system also contains other fluids, such as air, then the heat flux density will be less than in a real heat pipe, which contains only a single substance. Heat can still be transferred in this system by the evaporation and condensation of vapor however, the system is properly classified as a heat pipe thermosyphon. In this case, the system no longer convects, so it is not a usual "thermosiphon". In some situations the flow of liquid may be reduced further, or stopped, perhaps because the loop is not entirely full of liquid. A good thermosiphon has very little hydraulic resistance so that liquid can flow easily under the relatively low pressure produced by natural convection. ![]() Convection moves the heated liquid upwards in the system as it is simultaneously replaced by cooler liquid returning by gravity. This phenomenon of natural convection is known by the saying "heat rises". The warmer fluid will "float" above the cooler fluid, and the cooler fluid will "sink" below the warmer fluid. The warmer fluid on one side of the loop is less dense and thus more buoyant than the cooler fluid on the other side. The phenomenon of thermal expansion means that a temperature difference will have a corresponding difference in density across the loop. Natural convection of the liquid starts when heat transfer to the liquid gives rise to a temperature difference from one side of the loop to the other. Its purpose is to simplify the transfer of liquid or gas while avoiding the cost and complexity of a conventional pump. This circulation can either be open-loop, as when the substance in a holding tank is passed in one direction via a heated transfer tube mounted at the bottom of the tank to a distribution point-even one mounted above the originating tank-or it can be a vertical closed-loop circuit with return to the original container. Thermosiphoning also occurs across air temperature gradients such as those utilized in a wood fire chimney or solar chimney. Thermosiphoning is used for circulation of liquids and volatile gases in heating and cooling applications such as heat pumps, water heaters, boilers and furnaces. Thermosiphon (or thermosyphon) is a method of passive heat exchange, based on natural convection, which circulates a fluid without the necessity of a mechanical pump. Thermosyphon circulation in a simple solar water heater (not a working model there is no water supply to replenish the tank when the tap is used) ( March 2009) ( Learn how and when to remove this template message) Please help to improve this article by introducing more precise citations. Wolf, Sol.This article includes a list of general references, but it lacks sufficient corresponding inline citations. published by (Wiley Eastern Ltd., New Delhi, 1982), I, Chapter 3, p. Shukla, Thermal Model of Hot water System, ‘Reviews of Renewable Energy Sources’, ed. Mishra, Advance Renewable Energy Sources. ![]() Tiwari, Solar Energy: Fundamental, Design, Modelling and Applications, Narosa Publishing House, New Delhi and CRC Press, New York, 2004 Lunde, Solar Thermal Engineering, Chapter 7 (Wiley, New York, 1980), pp. ![]()
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