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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J: Thermal Management".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 14474

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Special Issue Editors

Dr. Steven Metcalf

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Guest Editor

School of Engineering, University of Warwick, Coventry CV4 7AL, UK
Interests: heat pumps; thermal storage; renewable energy

Dr. Angeles Rivero-Pacho

E-Mail Website
Guest Editor

School of Engineering, University of Warwick, Coventry CV4 7AL, UK
Interests: heat pumps; thermal storage; renewable energy

Special Issue Information

Dear Colleagues,

We are editing a Special Issue of Energies: ‘’Advances in Adsorption Heat Pumps, Stores, and Systems’’. This is a rapidly advancing field with important work taking place in many countries world-wide. Applications of interest include not only heat-driven heat pumps but thermal stores, refrigeration, air conditioning, heat transformers, and water harvesting, all of which utilise adsorption technology.

The scope includes open and closed systems, physical and chemical adsorption, and hydrides, and papers can range from basic thermodynamics, through materials, to laboratory systems and demonstrations.

Dr. Steven Metcalf
Dr. Angeles Rivero-Pacho
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

adsorption
heat pumps
refrigeration and air conditioning
thermal storage

Published Papers (6 papers)

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Research

29 pages, 42984 KiB

Open AccessArticle

Resorption Thermal Transformer Generator Design

by Samuel Hinmers, George H. Atkinson, Robert E. Critoph and Michel van der Pal

Energies 2022, 15(6), 2058; https://0-doi-org.brum.beds.ac.uk/10.3390/en15062058 - 11 Mar 2022

Cited by 4 | Viewed by 2142

Abstract

This work takes an empirical and evidence-based approach in the development of a resorption thermal transformer. It presents the initial modelling conducted to understand key performance parameters (coefficient of performance and specific mean power) before discussing a preliminary design. Experimental results from large temperature jump and isosteric heating tests have identified the importance of heat transfer in ammonia-salt systems. Both the heat transfer resistance between the salt composite adsorbent and the tube side wall, and the heat transfer from the heat transfer fluid to the tube side wall are key to realising resorption systems. The successful performance of a laboratory-scale prototype will depend on the reduction in these heat transfer resistances, and improvements may be key in future prototype machines. A sorption reactor is sized and presented, which can be scaled for length depending on the desired power output. The reactor design presented was derived using data on reaction kinetics constants and heat of reaction for calcium chloride reacting with ammonia that were obtained experimentally. The data enabled accurate modelling to realise an optimised design of a reactor, focusing on key performance indicators such as the coefficient of performance (COP) and the system power density. This design presents a basis for a demonstrator that can be used to collect and publish dynamic data and to calculate a real COP for resorption system. Full article

(This article belongs to the Special Issue Advances on Adsorption Heat Pumps, Stores and Systems)

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14 pages, 3169 KiB

Open AccessArticle

Testing of a Falling-Film Evaporator for Adsorption Chillers

by Tommaso Toppi, Tommaso Villa, Salvatore Vasta, Walter Mittelbach and Angelo Freni

Energies 2022, 15(5), 1709; https://0-doi-org.brum.beds.ac.uk/10.3390/en15051709 - 24 Feb 2022

Cited by 3 | Viewed by 1603

Abstract

In this work, the performance of an innovative evaporator based on water falling film was investigated. The studied evaporator has been equipped with a recirculation system to maximise the wetted surface. Tests have been carried out in a lab-scale adsorption unit connected to a test bench recently realised at Politecnico di Milano labs for evaluating heat transfer performances under realistic operating conditions. Several ad/desorption cooling cycles were performed, setting different liquid refrigerant initial contents (0.9–1.5 kg), different chilled water inlet temperatures (7–20 °C) and flow rates (200–1000 L/h) and different adsorbent bed temperatures (25–30 °C). Evaporation performance has been determined in delivered cooling capacity. Moreover, the experimental data were used to calculate the overall evaporator heat transfer conductance (UA). Experiments showed how the heat duty peaks are mainly due to the thermal level of the chilled water that enters the evaporator, not the water content inside it because this value only affects the duration of the process. Instead, the UA value does not depend on the evaporator inlet chilled water temperature and initial mass content inside the evaporator. UA is 540–570 W/K for temperatures of chilled water entering the evaporator, equal to 10–20 °C, and mass of refrigerant of 0.9–1.5 kg. Full article

(This article belongs to the Special Issue Advances on Adsorption Heat Pumps, Stores and Systems)

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19 pages, 4922 KiB

Open AccessArticle

Modeling and Analysis of a Coated Tube Adsorber for Adsorption Heat Pumps

by João M. S. Dias and Vítor A. F. Costa

Energies 2021, 14(21), 6878; https://0-doi-org.brum.beds.ac.uk/10.3390/en14216878 - 20 Oct 2021

Cited by 3 | Viewed by 1487

Abstract

This work investigates the effects of several parameters on the coefficient of performance (COP) and the specific heating power (SHP) of a coated-tube adsorber for adsorption heat pumps (AHP) suitable for water heating (space and/or domestic water heating). The COP and SHP are obtained based on physical models that have already been proven to adequately describe this type of adsorber. Several parameters are tested, namely, the regeneration, condenser and evaporator temperatures, the heat transfer fluid velocity, the tube diameter, the adsorbent coating thickness, the metal–adsorbent heat transfer coefficient, and the cycle time. Two different scenarios were tested, corresponding to distinct working conditions. The working conditions for Scenario A are suitable for pre-heating water in mild climates. Scenario B’s working conditions are based on the European standard EN16147. The maximum COP is obtained for regeneration temperatures of 75 °C and 95 °C for Scenarios A and B, respectively. The COP increases for longer cycle times (more complete adsorption and desorption processes) whilst the SHP decreases (less complete cycles by unit time). Hence, the right balance between the COP and the SHP must be found for each particular scenario to have the best whole performance of the AHP. A metal–adsorbent heat transfer coefficient lower than 200 W·m⁻²·K⁻¹ leads to reduced SHP. Lower adsorbent coating thicknesses lead to higher SHP and can still provide reasonably high COP. However, low coating thicknesses would require a too-high number of tubes to achieve the desired adsorbent mass to deliver the required useful heating power, resulting in too-large systems. Due to this, the best relationship between the SHP and the size of the system must be selected for each specific application. Full article

(This article belongs to the Special Issue Advances on Adsorption Heat Pumps, Stores and Systems)

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21 pages, 5287 KiB

Open AccessArticle

Ammonium Chloride (NH₄Cl)—Ammonia (NH₃): Sorption Characteristics for Heat Pump Applications

by George H. Atkinson, Samuel Hinmers, Robert E. Critoph and Michel van der Pal

Energies 2021, 14(18), 6002; https://0-doi-org.brum.beds.ac.uk/10.3390/en14186002 - 21 Sep 2021

Cited by 8 | Viewed by 3717

Abstract

In a resorption heat pump, the adsorption and desorption reaction of ammonium chloride (NH₄Cl) with ammonia (NH₃) is of interest as a Low Temperature Salt (LTS). Reviewing previously published NH₄Cl-NH₃ equilibrium lines, ammonium chloride appears to offer useable working temperatures (50–70 °C) in the 10–15 bar pressure range during the adsorption reaction, and provides beneficial working conditions for the desorption reaction, when compared with alternative LTS candidates at atmospheric pressure. The NH₄Cl-NH₃ adsorption and desorption reactions, using a NH₄Cl composite salt, have been evaluated under dynamic ‘real-world’ conditions in a Large Temperature Jump (LTJ) experimental testing rig; although there are concerns with mass transfer characteristics, the salt exhibits no hysteresis between the adsorption and desorption reactions, contrary to previous literature. The experimentally obtained equilibrium line values for the reaction enthalpy and entropy are 29,835 J/mol and 207 J/(mol∙K), respectively. Using a semi-empirical model, the NH₄Cl composite salt has been successfully characterised, enabling the prediction of salt reaction behaviour. The model constants, A and n, identified are 4.5 and 5 for adsorption and 5 and 4 for desorption, with an overall salt active fraction (applicable to both reactions) of 0.98. Overall, the working equilibrium line and the dynamic performance of ammonium chloride has been investigated and the applicability of NH₄Cl as a LTS for a resorption heat pump determined. Full article

(This article belongs to the Special Issue Advances on Adsorption Heat Pumps, Stores and Systems)

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17 pages, 6214 KiB

Open AccessArticle

Design and Large Temperature Jump Testing of a Modular Finned-Tube Carbon–Ammonia Adsorption Generator for Gas-Fired Heat Pumps

by Steven Metcalf, Ángeles Rivero-Pacho and Robert Critoph

Energies 2021, 14(11), 3332; https://0-doi-org.brum.beds.ac.uk/10.3390/en14113332 - 05 Jun 2021

Cited by 5 | Viewed by 2401

Abstract

Gas-fired heat pumps are a potential replacement for condensing boilers, utilizing fossil-fuel resources more efficiently and reducing the amount of biogas or hydrogen required in sustainable gas grids. However, their adoption has been limited due to their large size and high capital cost, resulting in long payback times. For adsorption-based heat pumps, the major development challenge is to maximize the rate of heat transfer to the adsorbent, whilst minimizing the thermal mass. This work develops a modular finned-tube carbon–ammonia adsorption generator that incorporates the adsorbent in highly compacted 3-mm layers between aluminum fins. Manufacturing techniques that are amenable to low cost and high-volume production were developed. The module was tested using the large temperature jump (LTJ) method and achieved a time constant for adsorption and desorption of 50 s. The computational model predicted that if incorporated into two adsorption generators of 6 L volume each, they could be used to construct a gas-fired heat pump with a 10 kW heat output and a gas utilization efficiency (GUE, the ratio of useful heat output to higher calorific value of gas used) of 1.2. Full article

(This article belongs to the Special Issue Advances on Adsorption Heat Pumps, Stores and Systems)

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24 pages, 5870 KiB

Open AccessArticle

Zeolite NaY-Copper Composites Produced by Sintering Processes for Adsorption Heat Transformation—Technology, Structure and Performance

by Andreas Velte, Jörg Weise, Eric Laurenz, Joachim Baumeister and Gerrit Füldner

Energies 2021, 14(7), 1958; https://0-doi-org.brum.beds.ac.uk/10.3390/en14071958 - 01 Apr 2021

Cited by 6 | Viewed by 1849

Abstract

In adsorption heat pumps, the adsorbent is typically combined with heat conducting structures in order to ensure high power output. A new approach for the direct integration of zeolite granules into a copper structure made of short copper fibers is presented here. Zeolite NaY granules with two different grain sizes are coated with copper fibers and powder and sintered to larger structures. The sorption dynamics of these structures were measured and evaluated in terms of heat and mass transfer resistances and compared to the loose grain configuration of the same material. We found that the thermal conductivity of such a composite structure is approximately 10 times higher than the thermal conductivity of an adsorbent bed with NaY granules. Sorption equilibrium measurements with a volumetric method indicate that the maximum uptake is not altered by the manufacturing process. Furthermore, the impact of the adsorbent–metal structure on the total thermal mass of an adsorption heat exchanger is evaluated. The price of the superior thermal conductivity is a 40% higher thermal mass of the adsorption heat exchanger compared to the loose grain configuration. Full article

(This article belongs to the Special Issue Advances on Adsorption Heat Pumps, Stores and Systems)

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