In this paper, the operating feasibility of a single-stage metal based hydride heat pump (SS-MHHP) working on the principle of crossed van't Hoff line concept is presented. The performance of the system is predicted by solving the unsteady, two-dimensional mathematical model in an annular cylindrical configuration employing two different hydride alloy pairs, namely, V 0.846Ti0.104Fe0.05/Fe0.9Mn 0.1Ti and V0.855Ti0.095Fe0.05/ MmNi4.7Al0.3 (regeneration alloy/refrigeration alloy). The influences of heat source (TH) and refrigeration (TC) temperatures on the amount of hydrogen transferred between the paired reactors, coefficient of performance (COP) and specific cooling power (SCP) of the crossed van't Hoff SS-MHHP system are studied. Within the selected ranges of operating temperatures, the COP of the crossed van't Hoff SS-MHHP is about 60% higher than the conventional single-stage MHHP. The optimum operating temperatures of V0.846Ti0.104Fe0.05/Fe0.9Mn 0.1Ti and V0.855Ti0.095Fe0.05/ MmNi4.7Al0.3 combinations are found to be 373/303/291 K and 400/303/283 K (heat source/heat sink/refrigeration temperatures), respectively. At the optimum operating temperatures, the COP and SCP of the V0.846Ti0.104Fe0.05/Fe0.9Mn 0.1Ti and V0.855Ti0.095Fe0.05/ MmNi4.7Al0.3 combinations are 0.89 and 30.8 W/kg of total mass and 0.86 and 30.3 W/kg of total mass, respectively. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Muthukumar M

Department of Structural and Geotechical Engineering

School of Civil Engineering

Vellore Campus

Satheesh A

Department of Thermal and Energy Engineering

School of Mechanical Engineering

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

International Journal of Hydrogen Energy

The requirement of simultaneous heating and cooling effects at different zones of a building demands for the development of an energy-efficient air-conditioning system for heating and cooling outputs. In order to fulfil this requirement, a novel multistage hydrogen-alloy–based sorption heat pump (H-A SHP) for space air-conditioning is proposed in the present work. The proposed system produces multiple cooling and heating outputs at 20°C and 45°C, respectively, with single heat input at 160°C. A set of MmNi5, La0.8Ce0.2Ni5, MmNi4.4Al0.6, and LaNi4.6Al0.4 metal hydrides (MHs) is chosen to operate at the above-mentioned temperature range with hydrogen as working fluid. The proposed system can completely eliminate the requirement of conventional compressor because it operates using waste heat, and useful outputs (cooling-heating) result from reaction enthalpies (MH + H2 interaction). The thermodynamic and heat-hydrogen transfer analyses of H-A SHP are carried out through finite volume approach, in which heat and mass transfer equations are solved to foresee the variations in MH bed temperature, hydrogen concentration, and heat interactions during cycle operation as well as the amount of cooling and heating outputs delivered to the air-conditioning space. The numerical code is validated with experimental pressure-concentration isotherms (PCIs) measured through Sievert's apparatus. The maximum heat exchange during the cooling and heating processes, at a particular instant of time, is observed as 257.5 and 286.1 W with cooling temperature of 10°C and heating temperature of 53°C, respectively. The thermodynamic performance is estimated as 178.5 kJ of cooling effect, 265.5 kJ of upgraded heat with overall coefficient of performance (COP) of 6.8, and overall specific alloy output of 396.5 W/0.34 kg of alloy. © 2019 John Wiley & Sons Ltd

International Journal of Energy Research

Thermodynamic and heat‐hydrogen transfer analyses of novel multistage hydrogen‐alloy sorption heat pump

The performance of metal hydrides based simultaneous cooling and heat transformation system (MHCHT) using a combination of La0.9Ce0.1Ni5–MmNi4.4Al0.6–MmNi3.7Co0.7Mn0.3Al0.3 hydrides is evaluated. The MHCHT is thermodynamically analysed using statically and dynamically measured PCIs and thermodynamic properties. In addition, a set of governing equations is solved in order to study the heat and hydrogen transfer between the reaction beds. The experimental PCI measurement data are compared with the numerical results and a reasonably good agreement is observed between them. From the results, the slope and hysteresis factors are determined for further thermal analyses. It is observed that the performance parameters i.e. cooling capacity, heat transformation capacity and coefficient of performance (COP) of MHCHT are significantly decreased by 42.4%, 26.7% and 19.1% respectively when dynamic property data are considered compared to static property data. In addition, the thermodynamic cycle is analysed by considering the variation in pressure during hydrogen transfer process between the metal hydride beds. © 2019 Hydrogen Energy Publications LLC

Performance analysis of metal hydride based simultaneous cooling and heat transformation system

The hydrogen absorption and desorption pressure-concentration isotherms (PCI) of La0.9Ce0.1Ni5 and LaNi4.6Al0.4 alloys are measured by static and dynamic method. The hydrogen absorption and desorption kinetics of the alloys also measured. The measured properties are used to study the performance of hydrogen based solid sorption heat transformer (MHHT). The thermodynamic simulation of MHHT is conducted using statically and dynamically measured PCI and thermodynamic properties. Due to variation in statically and dynamically measured metal hydride properties, significant variations in coefficient of performance (COP) and heat transformation capacity of MHHT are observed. In case of thermodynamic analysis using dynamically measured properties the heat transformation capacity and COP are decreased by 42.6% and 22.2% respectively, compared to statically measured data. This is due to the decrease in amount of hydrogen transmission and pressure differential between paired metal hydride reactors, and increase in reaction enthalpies. Later, the actual thermodynamic cycle for MHHT is constructed by considering the variation in pressure during hydrogen transfer processes between the metal hydride reactors. © 2017 Elsevier Masson SAS

Journal	Data powered by TypesetInternational Journal of Hydrogen Energy
Publisher	Data powered by TypesetElsevier BV
ISSN	0360-3199
Open Access	No