1,721,178 research outputs found
Pannelli solari termici piani operanti in cicli inversi a pompa di calore: Limiti e Prospettive
No full textCaratteristiche termiche del condensatore e prestazioni energetiche di cicli frigoriferi per uso domestico: aspetti termodinamici e tecnici associati al funzionamento intermittente
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Influenza delle proprietà termofisiche di alcuni polimeri estrusi durante i transitori termici nei processi di calibrazione
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A new procedure to measure water adsorption isotherms of porous fibrous materials
No full textAbstract
A typical relation between accumulated liquid, temperature, and vapour pressure characterizes any surface, in particular any porous structure. This relationship is usually described by means of ‘‘adsorption isotherms’’, which are functions that correlate the amount of liquid in the porous material to the partial pressure of its vapour, for a given constant temperature. Speaking about fibrous insulation materials or building materials, the fluid of interest is simply water. The knowledge of water adsorption isotherms is of great importance in the formulation of heat and mass transfer models inside moist bodies. Typical experimental techniques for adsorption isotherm evaluation (salt solution methods, climatic chamber methods, etc.) require the conteporary control of both temperature and relative humidity of the environment surrounding the specimen. This often results in the need of dedicated and expensive experimental set-ups. In this work the possibility to use a simpler apparatus to obtain the sorption-desorption characteristics of a body is investigated from the theoretical point of view by means of simulated experiments. The proposed measurement procedure uses a closed, non permeable system in which only temperature is to be controlled, while the total water content, liquid plus vapor, remains constant. The new procedure offers an additional benefit, since both the constant water and the constant dry air mass constraints are used as further a priori information to improve the precision of the estimated results
Experimental Heat Transfer of Drag Reducing Polymer Solutions in Enhanced Surface Heat Exchangers
No full textA set of previous termexperimentalnext term tests on the effect of polymeric additives in water are presented from the point of view of friction losses and previous termheatnext termprevious termtransfernext term performance variations, in single-passage countercurrent straight-pipe previous termheatnext termprevious termexchangersnext term. The tests were performed on smooth, finned, and grooved pipes of different diameters and show that the use of previous termpolymersnext term in augmented previous termsurfacenext termprevious termheatnext termprevious termexchangersnext term is generally not advisable. However, they also confirm that thermal bus systems as a whole can take advantage of previous termdragnext term-previous termreducingnext termprevious termpolymernext termprevious termsolutionsnext term, provided that accurate trade-off analyses are performed to get the best compromise between pressure losses and global previous termheatnext termprevious termtransfernext term performance of the thermal loop
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