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Downward two-phase flow applications for a non conventional heat pump
No full textA non-conventional heat pump working by a difference in density between two branches of a hydraulic vertical loop has been described. This system called thermogravimetric heat pump, TGHP, operates with a non-conventional regenerative thermodynamic cycle which remarkably improves COP values. The lower density in the ‘downward branch’ is obtained by a
liquid–vapour two-phase flow. Performances and main geometrical characteristic trends, such as plant height Z and two-phase column diameter DT–PD have been drawn, varying the minimum cycle temperature between 15 and 25 8C and the user temperature, Tmax; in the range 60–70 8C. The carrier fluid is demineralized water; according to the peculiar working fluid—PP50, HFC 134a and HFC 338cca—different solutions can be obtained, such as for 10–12 storey buildings or for skyscrapers. Yet, the results obtained with HFC 338cca must be accepted with some cautions while waiting for a better characterisation of such fluid. Chemical compatibility, thermal stability, environmental impact have been also taken into account in the choice of the operating couple, carrier fluid—working fluid. While the thermodynamic conversion process is non-conventional, the TGHP can be assembled by standardised technology. The compressor of a conventional plant is here replaced by a feeding pump and COP values obtained through a regenerative TGHP are globally larger than those of a common heat pump
Influence of two-phase flow on the performances of thermogravimetric heat pumps
No full textA non-conventional heat pump, the so-called Thermogravimetric Heat Pump TGHP, fundamentally based on an isothermal compression of a gas-liquid two-phase flow is analysed. The operating fluid couple consists of a carrier fluid constantly in liquid phase and of a working fluid that undergoes a thermodynamic cycle with a phase transition.
Thermodynamic aspect of a TGHP is definitely more convenient compared to a conventional compression HP; conversely, the partial evaporation of carrier fluid and fluid dynamic dissipative effects reduce the thermodynamic benefit and such reduction
can amount up to few percent even if homogeneous model is considered. The prevision of the energetic performances of TGHP is rather critical in that no correlation of void fraction are at present available for large duct diameters and for the range of gas fractions of volume flow typical of thermogravimetric heat pumps. In the present paper, the impact on TGHP performances due to uncertainties ensuing from different types of extrapolations regarding some experimental tests have been considered
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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