A bottom-up estimation of the heating and cooling demand in European industry

Energy balances are usually aggregated at the level of subsector and energy carrier. While heating and cooling accounts for half the energy demand of the European Union’s 28 member states plus Norway, Switzerland and Iceland (EU28 + 3), currently, there are no end-use balances that match Eurostat’s energy balance for the industrial sector. Here, we present a methodology to disaggregate Eurostat’s energy balance for the industrial sector. Doing so, we add the dimensions of temperature level and end-use. The results show that, although a similar distribution of energy use by temperature level can be observed, there are considerable differences among individual countries. These differences are mainly caused by the countries’ heterogeneous economic structures, highlighting that approaches on a process level yield more differentiated results than those based on subsectors only. We calculate the final heating demand of the EU28 + 3 for industrial processes in 2012 to be 1035, 706 and 228 TWh at the respective temperature levels > 500 °C (e.g. iron and steel production), 100–500 °C (e.g. steam use in chemical industry) and < 100 °C (e.g. food industry); 346 TWh is needed for space heating. In addition, 86 TWh is calculated for the industrial process cooling demand for electricity in EU28 + 3. We estimate additional 12 TWh of electricity demand for industrial space cooling. The results presented here have contributed to policy discussions in the EU (European Commision 2016), and we expect the additional level of detail to be relevant when designing policies regarding fuel dependency, fuel switching and specific technologies (e.g. low-temperature heat applications).     

Parametric analysis and yearly performance of a trigeneration system driven by solar‐dish collectors

Solar‐driven polygeneration systems are promising technologies for covering many energy demands with a renewable and sustainable way. The objective of the present work is the investigation of a trigeneration system, which is driven by solar‐dish collectors. The examined trigeneration system includes an organic Rankine cycle (ORC), which operates with toluene, and an absorption heat pump, which operates with LiBr/H₂O. The absorption heat pump is fed with heat by the condenser of the ORC, which operates at medium temperature levels (120°C to 150°C). The absorption heat pump produces both useful heat at 55°C and cooling at 12°C. The ORC produces electricity, and it is fed by the solar dishes. The examined ORC is a regenerative cycle with superheating. The total analysis is performed with a developed model in Engineering Equation Solver (EES). The system is investigated parametrically for different ORC heat‐rejection temperatures, different superheating levels in the turbine inlet, and various solar‐beam irradiation levels. Furthermore, the system is investigated on a yearly basis for the climate conditions of Athens (Greece) and for Belgrade (Serbia). It is found that the yearly system energy and exergy efficiencies are 108.39% and 20.92%, respectively, for Athens, while 111.38% and 21.50%, respectively, for Belgrade. The values over 100% for the energy efficiency are explained by the existence of a heat pump in the examined configuration. For both locations, the payback period is found close to 10 years and the internal rate of return close to 10%. The final results indicate that the examined configuration is a highly efficient and viable system, which operates only with a renewable energy source.     

Transient temperature distributions in canned products during heat sterilization and cooling

This reseach was performed using experimental temperature data and a simple analytical model to estimate the temperature distributions at the centres of cylindrically canned products (diameter/thickness ratio = 4/1) during heat sterilization and cooling under continuous flow conditions for two retort temperatures (115 and 121°C). The recorded experimental temperature data for an individual can for two different retort temperatures were then used to construct the dimensionless experimental centre temperature curves. In order to predict dimensionless centre temperature profiles with a mathematical model, the convection boundary condition (i.e. 0·1 < Bi < 100) in transient heat transfer was considered. The predicted temperature profiles were compared with the experimental centre temperature measurements for two cases—heat sterilization and cooling. The experimental temperature values were in very good agreement with the theoretical predictions. The results of this study show that the present technique is a reasonable tool for estimating in a simple and accurate form the temperature distributions of a cylindrically canned product subject to both heat sterilization and cooling.     

A synergetic hybridization of adsorption cycle with the multi-effect distillation (MED)

Multi-effect distillation (MED) systems are proven and energy efficient thermally-driven desalination systems for handling harsh seawater feed in the Gulf region. The high cycle efficiency is markedly achieved by latent energy re-use with minimal stage temperature-difference across the condensing steam and the evaporating saline seawater in each stage. The efficacies of MED system are (i) its low stage-temperature-difference between top brine temperature (TBT) and final condensing temperature, (ii) its robustness to varying salinity and ability to handle harmful algae Blooming (HABs) and (iii) its compact foot-print per unit water output. The practical TBT of MED systems, hitherto, is around 65 °C for controllable scaling and fouling with the ambient-limited final condenser temperature, usually from 30 to 45 °C.The adsorption (ADC) cycles utilize low-temperature heat sources (typically below 90 °C) to produce useful cooling power and potable water. Hybridizing MED with AD cycles, they synergistically improve the water production rates at the same energy input whilst the AD cycle is driven by the recovered waste heat. We present a practical AD + MED combination that can be retrofitted to existing MEDs: The cooling energy of AD cycle through the water vapor uptake by the adsorbent is recycled internally, providing lower temperature condensing environment in the effects whilst the final condensing temperature of MED is as low as 5–10 °C, which is below ambient. The increase in the temperature difference between TBT and final condensing temperature accommodates additional MED stages. A detailed numerical model is presented to capture the transient behaviors of heat and mass interactions in the combined AD + MED cycles and the results are presented in terms of key variables. It is observed that the water production rates of the combined cycle increase to give a GOR of 8.8 from an initial value of 5.9.     

Experimental investigation on a MnCl2–CaCl2–NH3 thermal energy storage system

Thermal energy storage (TES) is regarded as one promising technology for renewable energy and waste heat recovery. Among TES technologies, sorption thermal energy storage (STES) has drawn burgeoning attention due to high energy storage density, long-term heat storage capability and flexible working modes. Originating from STES system, resorption thermal energy storage (RTES) system is established and investigated for recovering the heat in this paper. The system is mainly composed of three high temperature salt (HTS) unit beds; three low temperature salt (LTS) unit beds, valves and heat exchange pipes. Working pair of MnCl₂–CaCl₂–NH₃ is selected for the RTES system. 4.8 kg and 3.9 kg MnCl₂ and CaCl₂ composite adsorbents are filled in the adsorption bed. Results indicate that the highest thermal storage density is about 1836 kJ/kg when the heat charging and discharging temperature is 155 °C and 55 °C, respectively. Volume density of heat storage ranges from 144 to 304 kWh/m³. The highest ratio of latent heat to sensible heat is about 1.145 when the discharging temperature is 55 °C. The energy efficiency decreases from 97% to 73% when the discharging temperature increases from 55 to 75 °C.     

Performance of a small‐scale compressed air storage (CAS)

The use of renewable energy, such as wind and solar, has significantly increased in the last decade. However, these renewable technologies have the limitation of being intermittent; thus, storing energy in the form of compressed air is a promising option. In compressed air energy storage (CAES), the electrical energy from the power network is transformed into a high‐pressure storage system through a compressor. Then, when the demand for electricity is high, the stored high‐pressure air is used to drive a turbine to generate electricity. The advantages of CAES are its high energy density and quality, and for being environmentally friendly process. In the existing facilities of University of Auckland, New Zealand, air cavern is not available; thus, a high‐pressure tank is used to store the compressed air, which could provide an excellent opportunity for small size applications. There is a limited literature available on the temperature and pressure profiles in a typical high‐pressure tank during charging and discharging processes. Therefore, this research investigates how temperature and pressure inside a high‐pressure tank change during charging and discharging processes. It will provide a better understanding for heat transfer in such system. Furthermore, it will provide the necessary information needed for the designing of an efficient small‐scale CAES. In this work, air is compressed to a maximum pressure of 200 bar and stored into a 2 L tank, which is fully fitted with a pressure transducer and a thermocouple suitable for high‐pressure measurements. The charging and discharging process is theoretically modeled, and the results are compared with the experimental measurements, showing a good agreement. The heat balance on the system is used to validate the steady‐state condition, while dynamic analysis is used to predict the transient change of compressed air and tank wall temperatures. The theoretical modeling is undertaken by solving the differential equations describing the transient change in temperature of both air and tank wall. The results of this study show that air temperature rises from 24°C to 60°C at 100 bar and from approximately 17°C to over 60°C at 200 bar. During discharging process, air temperature drops from ambient to 5°C at starting pressure of 100 bar and to ?20°C at starting pressure of 200 bar.     

中深层地热Ｕ型井地埋管换热器的试验研究

地热能作为一种非碳基能源,具有储量丰富、清洁可再生等特点,开发利用地热能有助于碳达峰的实现。在中深层地源热泵领域,我国主要以单井同轴管为主,而相对高效的中深层地热U型井地埋管案例屈指可数。为了了解中深层地热U型井地埋管换热性能及井下换热参数变化,完成了新型的Ｕ型井地埋管换热器工程,并在此基础上进行了实验研究。首先,开展了地温测量,确定了研究区的地层温度,根据热储的物性条件选取了水平井段及对接位置;其次,分析空载循环试验工况下循环水的流量及井下温度的变化情况,研究了负载工况下供回水温度、流量、换热量、不同井段对换热的贡献率、井下温度的动态变化、U型井的恢复能力等因素。实验结果表明,中深层Ｕ型井地埋管换热器井底温度会随运行时间增长而降低,流量大且回水温度较低的情况下,换热器的换热量比较高,最高为1336.8kW;回水井对换热量的增加有限,每百米增加0.12℃,实际工程中可以考虑减小口径,降低建设费用。U型井地埋管换热器的地温恢复能力较强,停止运行24h左右井底温度与初始温度差为-13℃。研究结果有助于研究人员对中深层Ｕ型井地埋管换热器有更进一步的认识,从而推动中深层地热能的健康可持续发展。     

GO-nafion composite membrane development for enabling intermediate temperature operation of polymer electrolyte fuel cell

Increasing Polymer Electrolyte Fuel Cells’ (PEFCs) operating temperature has benefits on the performance and the ease of utilisation of the heat generated; however, efforts for high temperature PEFCs have resulted in high degradation and reduced life time. In the literature, conventional low temperature (T < 80 °C) and high temperature (140–200 °C) regimes have been extensively studied, while the gap of operating at intermediate temperature (IT) (100–120 °C) has been scarcely explored.The main bottleneck for operating at IT conditions is the development of a suitable proton exchange membrane with comparable performance and lifetime to the commercially used Nafion operating at conventional conditions. In this work, composite membranes of Graphene Oxide (GO) and Nafion of varied thickness were fabricated, characterised and assessed for in-situ single cell performance under automotive operating conditions at conventional and intermediate temperatures.The material characterisation confirmed that a composite GO-Nafion structure was achieved. The composite membrane demonstrated higher mechanical strength, enhanced water uptake, and higher performance. It was demonstrated that by utilising GO-Nafion composite membranes, an up to 20% increase in the maximum power density at all operating temperatures can be achieved, with the optimum performance is obtained at 100 °C. Moreover, the GO-Nafion membrane was able to maintain its open circuit voltage values at increased temperature and reduced thickness, indicating better durability and potentially higher lifetime.     

Thermodynamic study of multistage absorption cycles using low‐temperature heat

The use of low‐temperature heat (between 50 and 90°C) is studied to drive absorption systems in two different applications: refrigeration and heat pump cycles. Double‐ and triple‐stage absorption systems are modelled and simulated, allowing a comparison between the absorbent–refrigerant solutions H₂O–NH₃, LiNO₃–NH₃ and NaSCN–NH₃. The results obtained for the double‐stage cycle show that in the refrigeration cycle the LiNO₃–NH₃ solution operates with a COP of 0.32, the H₂O–NH₃ pair with a COP of 0.29 and the NaSCN–NH₃ solution with a COP of 0.27, when it evaporates at ?15°C, condenses and absorbs refrigerant at 40°C and generates vapour at 90°C. The results are presented for double‐ and triple‐stage absorption systems with evaporation temperatures ranging between ?40 and 0°C and condensation temperatures ranging from 15°C to 45°C. The results obtained for the double‐stage heat pump cycle show that the LiNO₃–NH₃ solution reaches a COP of 1.32, the NaSCN–NH₃ pair a COP of 1.30 and the H₂O–NH₃ mixture a COP of 1.24, when it condenses and absorbs refrigerant at 50°C, evaporates at 0°C and generates vapour at 90°C. For the double‐ and triple‐stage cycles, the results are presented for evaporation temperatures ranging between 0 and 15°C. The minimum temperature required in the generators to operate the refrigeration and heat pump cycles are also presented. Copyright © 2002 John Wiley & Sons, Ltd.     

Liquid organic hydrogen carriers (LOHCs) in the thermochemical waste heat recuperation systems: The energy and mass balances

This paper is presented a concept of thermochemical recuperation of waste heat based on hydrogen extraction from liquid organic hydrogen carriers (LOHC), on the example of methylcyclohexane-toluene system. The advantages of this concept is described, for example, a possibility to use a moderate low temperature of waste heat for generation high-exergy “green” hydrogen fuel. To understand the effect of operating parameters on the energy and mass balance, the thermodynamic analysis was performed. The chemical system for hydrogen generation was analyzed via Gibbs free energy minimization method. The thermodynamic analysis was conducted under various operating conditions: temperature of 100–400 °C, pressure of 1–4 bar. Aspen HYSYS software was used for the energy and mass conservation analysis. Sankey diagram for the energy flows is depicted. The results showed that the maximum energy efficiency the thermochemical waste heat recuperation system have in the temperature range above 300–350 °C. In this temperature range, the effect of pressure on the energy balance is negligible and it is recommended for the thermochemical recuperation system to use LOHC with a pressure of 1.5–2 bar. Based on the analysis, it was concluded that the temperature potential of waste heat for about 300–350 °C is enough for the investigated concept. An analysis of a mass balance showed that the decreasing in condensation temperature leads to a significant increasing in the share of condensed toluene from toluene-hydrogen mixture after a reactor. If temperature of a hydrogen-toluene mixture of 20 °C at pressure above 2 bar about 96% of toluene can be condensed after the first condenser.     

Turkey's industrial waste heat recovery potential with power and hydrogen conversion technologies: A techno-economic analysis

In this study an investigation of Turkey's overall industrial waste heat potential is conducted, and possible power and hydrogen conversion technologies are considered to produce useful energy such as power and hydrogen. The annual total industrial waste heat was has a 71 PJ in 2019 and is expected to double by 2050. The temperature range of the waste heat differs by sector at a large range of 50 °C–1000 °C. Absorption power cycle (APC), Organic Rankine Cycle (ORC), Steam Rankine cycle (SRC) and Gas Turbine (GT) systems are adapted for power production based on the waste heat temperature while electrochemical and electro-thermochemical hydrogen production systems are adapted for hydrogen generation. Proton Exchange Membrane, Alkaline, and high temperature steam electrolysis methods are selected for pure electrochemical conversion technologies and Hybrid Sulfur (HyS), Copper Chlorine (CuCl), Calcium–Bromine (CaBr), and Magnesium Chlorine (MgCl) cycles are utilized as hybrid thermochemical technologies. Many cases are formed, and best temperature matching power-hydrogen system couples are selected. It is possible to produce enough hydrogen to compensate up to 480 million m³ natural gas equivalents of hydrogen annually with selected technologies which corresponds to ~5% of residential natural gas consumption in Turkey. Economic analysis reveals that lowest hydrogen generation cost belongs to the GT-HyS system. When hydrogen is used for heating applications by a certain mixture fraction to NG pipelines, it may reduce more than 720 thousand tons of CO₂ reduction annually due to natural gas use.     

Energy policy and the role of bioenergy in Poland

Poland, as many other countries, has ambitions to increase the use of renewable energy sources. In this paper, we review the current status of bioenergy in Poland and make a critical assessment of the prospects for increasing the share of bioenergy in energy supply, including policy implications. Bioenergy use was about 4% (165 PJ) of primary energy use (3900 PJ) and 95% of renewable energy use (174 PJ) in 2003, mainly as firewood in the domestic sector. Targets have been set to increase the contribution of renewable energy to 7.5% in 2010, in accordance with the EU accession treaty, and to 14% in 2020. Bioenergy is expected to be the main contributor to reaching those targets. From a resource perspective, the use of bioenergy could at least double in the near term if straw, forestry residues, wood-waste, energy crops, biogas, and used wood were used for energy purposes. The long-term potential, assuming short rotation forestry on potentially available agricultural land is about one-third, or 1400 PJ, of current total primary energy use. However, in the near term, Poland is lacking fundamental driving forces for increasing the use of bioenergy (e.g., for meeting demand increases, improving supply security, or further reducing sulphur or greenhouse gas emissions). There is yet no coherent policy or strategy for supporting bioenergy. Co-firing with coal in large plants is an interesting option for creating demand and facilitating the development of a market for bioenergy. The renewable electricity quota obligation is likely to promote such co-firing but promising applications of bioenergy are also found in small- and medium-scale applications for heat production. Carbon taxes and, or, other financial support schemes targeted also at the heating sector are necessary in the near term in order to reach the 7.5% target. In addition, there is a need to support the development of supply infrastructure, change certain practices in forestry, coordinate RD&D efforts, and support general capacity building. The greatest challenge for the longer term lies in reforming and restructuring the agricultural sector.     

Study on 2‐propanol/acetone/hydrogen chemical heat pump: endothermic dehydrogenation of 2‐propanol

Low‐temperature thermal energy can be upgraded to higher temperatures by chemical heat pumps. Among the working pairs for chemical heat pumps, 2‐propanol/acetone/hydrogen using a combination of dehydrogenation (of 2‐propanol)/ hydrogenation (of acetone) reaction seems to be promising. This study was aimed at experimentally determining the performance of dehydrogenation of 2‐propanol using a 10 wt% Ru–Pt/activated C catalyst in a temperature range 60–80 °C with a view to study the influence of reaction temperature, catalyst concentration, nitrogen flow, and acetone concentration in liquid reactant on 2‐propanol dehydrogenation in terms of reaction rate and hydrogen produced. The maximum initial reaction rate of 54 mmol h⁻¹ g⁻¹ was obtained at a reaction temperature of 75–80 °C and a catalyst concentration of 1.3 g l⁻¹. Observations indicate that at constant reaction temperature and catalyst concentration, varying amounts of catalyst and 2‐propanol resulted in different reaction rates. The reaction rate decreases with increasing acetone in liquid reactant. The nitrogen flow strongly influences the reaction rate, as it is used as a stirring medium. The maximum heat utilization of 4.5 per cent was obtained when the oil bath temperature was 100 °C at a catalyst concentration of 1.3 g l⁻¹. Copyright © 2000 John Wiley & Sons, Ltd.     

Thermodynamic analysis and experimental validation of multi-composition ammonia liquor absorption engine cycle for power generation

Energy conservation, utilization, and effective integration are of utmost importance for future sustenance. Accordingly, this work focuses on the generation of power from the low-grade temperature below 150°C . A proposed novel multi-composition ammonia liquor absorption engine (MALAE) power cycle can be used toward the above purpose by supplying renewable energy obtained from low concentration type solar collectors. Proposed MALAE power cycle minimizes heal loss due to heat recovery and uses high purity NH₃ vapors to expand through the isentropic turbine. MALAE power system is modeled and simulated using NH₃-H₂O as a working fluid for a reboiler temperature of 115°C . The purpose of this work is to simulate the proposed MALAE power cycle with the distillation column and two solution heat exchanger (SHE). MALAE modeling and simulation is accomplished in SCILAB software. The simulation outcome is validated with the pilot-scale 5 kW experimental setup and validation showed ±5% deviation. A comparison of MALAE cycle with published cycles signifies higher efficiency of MALAE cycle toward the utilization of low-grade energy from a temperature range of 100°C to 150°C . Finally, detailed parametric analysis of MALAE cycle efficiency is presented in terms of number of plates, distillation pressure and vapor flowrate, absorber temperature, pressure partial condenser temperature, and heat loads.     

Hybrid heating system for increased energy efficiency and flexible control of low temperature heat

This study presents the evaluation of functionality and potential of a hybrid heating system (H²S) prototype. This technology is designed for retrofitting thermal treatment plants to use hot water (HW) and steam in controlled ratios. In the food industry, steam with a temperature above 140 °C usually indirectly supplies the thermal production processes, but most of them only require temperatures below 100 °C. Total site heat integration is applied on a cheese and whey powder plant to show the potential for low-temperature heat (below 100 °C) that could be supplied more appropriately by hot water cogeneration, heat recovery and heat pumps. These low-temperature heat sources can only be combined with the rigid steam system if the demand structure is changed to a hybrid use of HW and steam. The H²S increases the energy efficiency and flexibility by integrating low-temperature heat and responding to sudden changes in the demand and supply structure, like demand response strategies on intermittent renewable energies and the changing availability of HW and steam. The technical implementation is realised by a hydraulic interconnection of heat exchangers and valves. A smart control algorithm acutely determines the share of HW and steam. Prerequisite for functional verification on a laboratory scale is a hardware-in-the-loop (HIL) testbed, in which load profiles and relevant process parameters are passed in real time between hardware components and simulation. The results show that the H²S is a feasible solution for maintaining product quality and safety while also increasing energy efficiency and energy flexibility.     

Performance analysis and validation on transportation of heat energy over long distance by ammonia–water absorption cycle

This paper presents the thermodynamic and hydrodynamic feasibility of the application of the ammonia–water absorption system for heat or cold transportation over long distance. A model of a long‐distance heat energy transportation system is built and analyzed, and it shows satisfactory and attractive results. When a steam heat source at the temperature of 120°C is available, the user site can get hot water output at about 55°C with the thermal COP of about 0.6 and the electric COP of about 100 in winter, and cold water output at about 8°C with the thermal COP of about 0.5 and the electric COP of 50 in summer. A small‐size prototype is built to verify the performance analysis. Basically the experimental data show good accordance with the analysis results. The ammonia–water absorption system is a potential prospective solution for the heat or cold transportation over long distance. Copyright © 2009 John Wiley & Sons, Ltd.     

Spatial modelling of industrial heat loads and recovery potentials in the UK

This paper presents a spatial model of industrial heat loads and technical recovery potentials in the UK, by recourse to energetic and exergetic analysis methods. The aims were to categorise heat users into broad temperature bands; quantify heat usage and wastage at different temperatures; and to estimate the technical potential for heat recovery based on current technologies (whilst ignoring spatial and temporal constraints). The main data source was the UK National Allocation Plan for the EU Emissions Trading Scheme, supplemented by capacity/output and specific energy consumption data for certain heterogeneous sectors. Around 60% of industry has been covered in terms of energy use, and 90% of energy-intensive sectors. The total annual heat use for these sectors was estimated at 650 PJ, with technically feasible annual savings in the region 36–71 PJ. This is in agreement with the only extant estimates for heat recovery from industrial processes, which are 65 and 144 PJ, respectively.     

Catalyst-assisted chemical heat pump with reaction couple of acetone hydrogenation/2–propanol dehydrogenation for upgrading low-level thermal energy: Proposal and evaluation

A chemical heat pump for upgrading low-level thermal energy has been proposed by adopting a reversible organic reaction couple, endothermic liquid-phase dehydrogenation of 2–propanol at low temperature and exothermic gas-phase hydrogenation of acetone at high temperature, where thermodynamical work is done by separating condensed 2–propanol from the gaseous mixture of 2–propanol, acetone and hydrogen in a fractionation column. In the system constitution of the continuous type, the overhead vapour of the fractionation column is fed through the heat exchanger into the exothermic reactor, where acetone and hydrogen in excess are changed at 200°C into the equilibrium mixture, from which condensable 2–propanol is separated in the column by cooling at 30°C. The reverse reaction of 2–propanol decomposition into acetone and hydrogen proceeds in the endothermic reactor, i.e. the reboiler of the column, absorbing heat at 80°C. On the contrary, acetone and hydrogen in the overhead vapour of the fractionation column are stored at 30°C as liquid and metal hydride, respectively, in the system constitution of the storage type; when necessary, metal hydride is decomposed by heating at 80°C, with hydrogen at high pressure evolved and fed through the heat exchanger into the exothermic reactor, giving the equilibrium mixture at high pressure and temperature. Product condensates are transferred through a valve into the fractionation column in order to separate 2–propanol and acetone, the former of which is dehydrogenated in the endothermic liquid-phase reactor, regenerating acetone and hydrogen at 80°C and atmospheric pressure. Energy efficiencies were evaluated for the system constitutions of both the continuous and storage types; the 80°C heat supplied was convertible into the 200°C heat continuously at the enthalpy efficiency or coefficient of performance (COP) of 0·36 in the former, whereas the 270°C heat was obtainable with the aid of metal hydride from the same heat source at COP of 0·21 in the latter.     

Effect of the plate thermal resistance on the heat transfer performance of a corrugated thin plate heat exchanger

Two‐dimensional conjugate conduction/convection numerical simulations were carried out for flow and thermal fields in a unit model of a counter‐flow‐type corrugated thin plate heat exchanger core. The effects of the thermal resistance of the solid plate, namely the variation of the plate thickness and the difference of the plate material, on the heat exchanger performance were examined in the Reynolds number range of 100<Re<400. Higher temperature effectiveness was obtained for a thicker plate at any Reynolds number, which was a unique feature of corrugated thin plate geometry. Detailed discussions on the thermal fields revealed that restricting the heat conduction along the plate by making the plate thinner or choosing a low thermal conductivity material causes a larger plate temperature variation along the plate, and, consequently, a smaller amount of thermal energy exchanged between two fluids. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(3): 209–223, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20110     

Magnesium oxide/water chemical heat pump to enhance energy utilization of a cogeneration system

A chemical heat pump using a magnesium oxide/water reaction system is expected to be applicable to cogeneration systems using gas engine, diesel engine, and fuel cells. The operability of the heat pump was examined experimentally under hydration operation pressures between 30 and 203 kPa. In the experiment, a reactant having high durability for repetitive operation was packed in a cylindrical reactor. The cycle of operation was repeated under various thermally driven operation conditions. The forward and reverse reactions were studied by measuring the reactor bed temperature distribution and the reacted fraction changes. The reactor bed stored heat at around 300–400 °C by the dehydration reaction and released heat at around 100–200 °C by the hydration reaction under the heat amplification mode operation. The practical possibility of the reactor bed was discussed based on the experimental results. The heat pump is expected to be applicable for load leveling in a cogeneration system by chemically storing surplus heat during low heat demand and supplying heat during peak demand. It was shown that the chemical heat pump would be able to improve the efficiency of energy utilization in cogeneration systems while also helping to reduce energy consumption and global carbon dioxide emissions.