1,073,636 research outputs found

    Modelling of shaded and unshaded shallow-ground heat pump system for a residential building block in a Mediterranean climate

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    Heat pumps may be coupled to shallow-ground geothermal fields and used for the purpose of space heating and cooling of buildings. However, quite often it is not possible to locate the geothermal field in cleared grounds, especially in cities where building density is high and land has a high premium. This leads to the possibility of burying the geothermal field under the basement of new building blocks, before construction of the building. In the present work, the shaded-unshaded arrangement is numerically studied by coupling the software DesignBuilder-EnergyPlus to assess the building's energy requirement with the software FEFLOW to solve the heat transfer equation in porous media. Assuming a standard residential building block, the coupling between the two software is performed by assigning the thermal energy requirement for air conditioning, as calculated by EnergyPlus, to a flat-panel typology of ground heat exchanger simplified in a 2D FEFLOW's domain. The results show that it is necessary to opt for a dual-source heat pump (air/geothermal) system to ensure that the ground is not frozen or over-heated at peak times and to improve the overall performance of the system.peer-reviewe

    Three-dimensional Navier-Stokes heat transfer predictions for turbine blade rows

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    Results are shown for a three-dimensional Navier-Stokes analysis of both the flow and the surface heat transfer for turbine applications. Heat transfer comparisons are made with the experimental shock-tunnel data of Dunn and Kim, and with the data of Blair for the rotor of the large scale rotating turbine. The analysis was done using the steady-state, three-dimensional, thin-layer Navier-Stokes code developed by Chima, which uses a multistage Runge-Kutta scheme with implicit residual smoothing. An algebraic mixing length turbulence model is used to calculate turbulent eddy viscosity. The variation in heat transfer due to variations in grid parameters is examined. The effects of rotation, tip clearance, and inlet boundary layer thickness variation on the predicted blade and endwall heat transfer are examined

    Eksplorasi Teknik Heat Transfer Printing dengan Zat Warna Dispersi pada Kain Sintetis

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    Seiring perkembangan jaman dan teknologi, perkembangan pada industri tekstil pun turut berkembang. Setelah tekstil sintetis berkembang di industri tekstil pada tahun 1920-an, teknik pengolahannya pun turut mengalami perkembangan dikarenakan tekstil sintetis memiliki sifat hydrophobic dan thermoplastic. Zat warna yang dirasa cocok untuk mewarnai tekstil sintetis adalah zat warna disperse yang berkembang pada awal tahun 1940. Kemudian ditemukan suatu teknik olah latar tekstil tersebut setelah beberapa percoban dengan zat warna disperse di tahun yang sama. Percobaan yang dilakukan didasari oleh sifat zat warna disperse yang ringan dan mudah tersublimasi jika terkena panas, didukung oleh sifat tekstil sintetis yang thermoplastic yaitu tenunannnya memiliki tendensi untuk meregang ketika terkena panas dan tekanan. Zat warna dispersi diwarnai diatas medium kertas yang kemudian diletakkan diatas kain sintetis kemudian diberikan perlakuan panas dan tekanan. Zat warna disperse yang tersublimasi akan berpindah dari kertas masuk ke pori-pori kain sintetis yang sedang meregang dan saat temperatur kembali pada suhu normal, struktur kain akan kembali ke sedia kala dan mengikat zat warna pada permukaan kain. Sehingga heat transfer printing menjadi salah satu teknik tekstil modern untuk reka latar kain sintetis

    Near-field radiative heat transfer between macroscopic planar surfaces

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    Near-field radiative heat transfer allows heat to propagate across a small vacuum gap in quantities that are several orders of magnitude greater then the heat transfer by far-field, blackbody radiation. Although heat transfer via near-field effects has been discussed for many years, experimental verification of this theory has been very limited. We have measured the heat transfer between two macroscopic sapphire plates, finding an increase in agreement with expectations from theory. These experiments, conducted near 300 K, have measured the heat transfer as a function of separation over mm to μ\mum and as a function of temperature differences between 2.5 and 30 K. The experiments demonstrate that evanescence can be put to work to transfer heat from an object without actually touching it

    Heat transfer, condensation and fog formation in crossflow plastic heat exchangers

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    In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall condensation and fog formation are considered in some detail. Separate attention is paid to the heat transfer and condensation of pure steam in the heat exchanger. Finally, the experiments performed are reported and the results compared with the models presented. From this comparison it can be learnt that the models are well able to predict the rate of heat transfer and phenomena such as condensation and fog formation

    Modelling thermal effects in agitated vessel and reactor design consideration

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    The knowledge of the heat transfer coefficient on the inner side of a heated vessel wall is of utmost importance for the design of agitated vessels. The present contribution deals with heat transfer in an agitated vessel containing non-Newtonian liquid. The impellers used are six-blade Turbine (TPD) and a Propeller (TPI). The following aspects are discussed: description of the heat transfer process with the aid of dimensional analysis, heat transfer correlations for agitated liquid and influence of impeller speed on heat transfer

    Hidden heat transfer in equilibrium states implies directed motion in nonequilibrium states

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    We study a class of heat engines including Feynman's ratchet, which exhibits a directed motion of a particle in nonequilibrium steady states maintained by two heat baths. We measure heat transfer from each heat bath separately, and average them using a careful procedure that reveals the nature of the heat transfer associated with directed steps of the particle. Remarkably we find that steps are associated with nonvanishing heat transfer even in equilibrium, and there is a quantitative relation between this ``hidden heat transfer'' and the directed motion of the particle. This relation is clearly understood in terms of the ``principle of heat transfer enhancement'', which is expected to apply to a large class of highly nonequilibrium systems.Comment: 4 pages, 4 figures; revise

    Heat transfer device

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    An improved heat transfer device particularly suited for use as an evaporator plate in a diffusion cloud chamber. The device is characterized by a pair of mutually spaced heat transfer plates, each being of a planar configuration, having a pair of opposed surfaces defining therebetween a heat pipe chamber. Within the heat pipe chamber, in contiguous relation with the pair of opposed surfaces, there is disposed a pair of heat pipe wicks supported in a mutually spaced relationship by a foraminous spacer of a planar configuration. A wick including a foraminous layer is contiguously related to the external surfaces of the heat transfer plates for uniformly wetting these surfaces
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