Industry sector within the European Union (EU) accounts for approximately 25 % of final energy use, where the steel industry accounts for 10 % of the total energy consumption in the industry sector. The steel industry and similar process industries are facing significant challenges to reduce their greenhouse gas emissions due to recent climate change legislations. One method to achieve this, is via the implementation of waste heat recovery systems. The paper presented focuses on a steel plant located in Slovenia, where significant amounts of thermal energy are lost through exhaust gases from a natural gas furnace. The novel multi-sink gravity-assisted Heat Pipe Heat Exchanger (HPHE) aims to recover and reuse waste heat and generates two useful heat sinks. The novel HPHE consists of air and water heat sink sections with an average energy recovery efficiency of 47 %. The recovered energy from the air section provides preheated combustion air to the burners, whereas the recovered energy from the water section opens the possibility for district heating. The thermosyphons in the exhaust-air section were arranged in a counterflow arrangement with Dowtherm A and distilled water as the working fluid, whereas the exhaust-water sections were arranged in a crossflow, with distilled water as the working fluid. The novel HPHE features a bypass, allowing complete flexibility for the end user to deactivate the exhaust-water section. To ensure replicability of the HPHE, a theoretical model has been developed and validated through experimental results, the model exhibited a good agreement with the results within an error of 15 %. Both air and water sections recovered 1677 MWh and 753 MWh annually, operating at 8050 and 5750 h respectively. The implementation of the HPHE equates to an overall reduction in CO2 emissions of 334 tCO2 per annum. Moreover, the unit highlights a benchmark for the technology due to its readiness within industry due to a reported Return on Investment (ROI) of under 10 months.

An analysis of the end use of energy in the EU reveals that industry is one of the three dominant categories, which accounts for 26.1% of the final end use of energy. In the case of the aluminium industry, approximately 70% of energy consumption is due to heat and thermal processes, highlighting a vast potential for waste heat recovery technologies. Within the aluminium die casting industry, liquid aluminium is cast, formed, cooled, and further processed within a thermal heat process, which includes three sub-processes: solubilising, quenching, and ageing. In the case presented, a thermal heat process is the second most energy intensive process within the factory, and the ageing heat treatment furnace accounts for 15% of the thermal heat process. The thermal heat treatment generates a significant amount of waste heat. The recovery of that waste heat, with minimal risk of cross contamination between streams and reduced chance of equipment failure, has been achieved via the use of a heat pipe heat exchanger (HPHE). The HPHE has been designed, manufactured, and installed in the solution furnace exhaust stack. The HPHE was designed to recover up to 88.6 kW in steady state operating conditions at 400 degrees C. The return on investment has been evaluated at 35 months with an expected CO2 emissions reduction of 86 tCO2/year when best engineering practices are applied. Furthermore, a theoretical modelling tool to predict the thermal performance of the HPHE was developed and validated within a +/- 20% deviation from the experimental results. This paper further presents the development of the theoretical model to allow a characterisation of HPHE technology and will act as a guideline for the design of HPHEs within the aluminium industry.

As policies have been implemented globally to limit the production of greenhouse gases (GHGs) and the effects of climate change, the generation of electricity by renewable technologies has started to increase. The development of sustainable energy storage solutions has also become more important. The continued use of conventional chemical batteries presents environmental issues such as heavy metal pollution and the use of unsustainable resources.An environmental Life Cycle Assessment (LCA) has been conducted to analyse the environmental impact of an innovative Thermal Battery (TB) and was compared with the impact of a Lithium Iron Phosphate Battery (LIPB) using a “cradle-to-gate” approach to establish the system boundaries. The study used the findings from existing literature to determine the environmental impact of the LIPB. The life cycle inventory for the TB was constructed based on a model and available literature. In this regard, the two products were compared on 10 impact categories, and the results indicated that the TB performed better in 8 categories on average. The highest impact observed from the TB was in terrestrial ecotoxicity, where it emitted above 7000 times more than the LIPB, amounting to approximately 0.0153 after normalisation. The highest normalised environmental load in the study was indicated to be in the category of marine ecotoxicity by the LIPB at 0.27, which was significantly higher than any load for the TB. Overall, the results obtained are encouraging for the TB, but it is recommended that a field study is completed to verify the assumptions made in this paper and to achieve a better comparability with studies conducted similarly.

In this paper, the performance of a multi-pass heat pipe-based heat exchanger (HPHE) is investigated experimentally and theoretically. The heat pipe system consists of copper heat pipes in a specific equatorially staggered configuration to facilitate heat transportation from a hot gas (air) to a water flow, which cools the condenser section of these heat pipes. The effect of the Reynolds number on the heat transfer rate was studied by altering the number of passes for the evaporator section for the same system by the incorporation of various baffles and by varying the water flow rate. The experimental results have highlighted the strong correlation between heat exchanger performance and the Reynolds number. By increasing the number of passes from one to five, the effectiveness of the HPHE was improved by more than 25%. It has been demonstrated that increasing the number of passes increases the Reynolds number of the flow, leading to higher heat transfer coefficients and lower thermal forced convection resistances. The HPHE overall performance, as well as, the outlet temperatures of the fluids were predicted through two theoretical models, based on the Log Mean Temperature Difference (LMTD) method and the Effectiveness-Number of Transfer Units (epsilon-NTU) method. The predictions were compared with experimental results and the accuracy of the models reported. The validation showed that the developed iterative LMTD model predicted the performance of the HPHE within 15.5% error. In comparison, the epsilon-NTU model predicted the total effectiveness with a maximum error of 19% and was able to predict the outlet temperatures of both air and water streams within an accuracy of +/- 0.7 degrees C. The reported research is of importance for the application of heat pipe heat exchangers in waste heat recovery. Finally, knowledge is provided on the accuracy of the available prediction models. (C) 2020 Elsevier Ltd. All rights reserved.

The ceramics industry is the second largest energy consuming sector in Europe. The main energy used in the ceramics industry is heat generated through burners using natural gas. The main area can be identified in three stages, the drying stage and the firing stage, and the cooling stage. The firing stage represents about 75% of the total energy cost. The roller hearth kiln technology is considered to be the most cost-effective solution for ceramic tile manufacturing. The kiln is separated into two sections, the firing stage and the cooling stage. The cooling stage generates large amounts of waste heat as the exhaust of the kiln is composed of a challenging flue gas for heat recovery. The recovery of this heat in an efficient way with no cross contamination has been achieved with a heat pipe heat exchanger (HPHE) system, which was designed, manufactured and installed on a roller hearth kiln and is presented in this paper. The heat pipe heat exchanger located next to the cooling section exhaust stack managed to recover up to 100 kW at steady state without cross contamination or excess fouling. The return on investment of the system has been evaluated at 16 months with a saving of 30,000 pound per year. This paper will present a deep row by row theoretical analysis of the heat pipe heat exchanger. The Computational Fluids Dynamics will also be presented to investigate the fluid dynamics within the evaporator and condenser section. Both investigations have then been validated by the experimental investigation carried out on a full-scale industrial system. The design approach used in this paper will highlight the benefits of this type of technology and provide a guideline for the design of novel heat pipe heat exchangers. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The development of waste heat recovery technologies has surged as a result of climate change initiatives, which require energy intensive industries to curb their emissions and lower energy consumption. Installing heat pipe heat exchangers has proven to be a reliable and effective method of recovering waste heat due to their passive operation, superconductive properties and small footprint. This paper highlights the application of a vertical multi-pass heat pipe heat exchanger to a lab scale ceramic kiln system used to transfer heat from the kiln exhaust to water. The innovative heat pipe heat exchanger exists as a novel variable unit able to recover heat energy for a range of inlet temperatures and flow rates. The installed unit has shown a heat recovery rate of up to 63 kW. A range of exhaust gas temperatures from 135 to 270 degrees C were trialled at varying heat source and sink mass flow rates. The results of the experiments as well as simulation results using a model built using the software TRNSYS are given. The investigation has confirmed that the TRNSYS simulation results agree well with the experimental results. Additionally, return on investment analysis predicted 33 months payback for a theoretical full-scale unit preheating water for space heating. (C) 2020 Elsevier Ltd. All rights reserved.

In this paper, the performance of a heat pipe based thermal management technique for batteries has been investigated experimentally. In this regard, a test rig was developed and used to demonstrate the effectiveness of flat heat pipe (heat mat) technology at controlling and maintaining the temperature of a prototype battery module, which consisted of sixteen prismatic lithium-titanate (LTO) cells. Test results were obtained which proved the ability of the technology to keep the battery cells at an optimal temperature, during cycling representative of real-world operation, from either a cold or hot start. The heat mat was shown to efficiently absorb the heat generated by the cells and transfer it effectively to an external cooling medium of either water or refrigerant. In conclusion, it was demonstrated that the maximum cell temperature is significantly reduced and the overall temperature uniformity of the module is greatly improved, when compared to a module with no thermal management. The maximum cell temperature was kept below 28 °C and the module temperature uniformity was maintained at +/−1 °C. By using test cycles that generated a quasi-steady-state heat load from the cells, it was shown that approximately 60% of the heat generated by the cells was removed by the heat mat. The results obtained from this work demonstrate that heat mat technology can improve battery performance and longevity by reducing the degradation and ageing process and cell imbalances, that result from high cell temperatures and module/pack-level temperature non-uniformity.

With the objective of estimating the pool boiling resistance of two-phase closed thermosyphons (TPCTs), the work presented gives the state of the art of nucleate pool boiling correlations. A deep analysis of up-to-date equations reported for bubbles and nucleate boiling is carried out and recommendations are provided to select the most suitable and reliable mathematical models. After introducing the operation of thermosyphons, a section dedicated to bubbles provides basic knowledge on nucleation processes and bubble growth. The main boiling mechanisms occurring in thermosyphons with a filling ratio of 100%, i.e. pool boiling, are explained in a comprehensive way. The current state of the art of correlations predicting the number of active nucleation sites, the bubble departure diameters and bubble departure frequencies is presented. In addition, 27 correlations of nucleate pool boiling heat transfer coefficients are critically reviewed. For all sections, the advised correlations are reported in a clear and simple way using tables. The aim of this paper is to provide sufficient knowledge on two-phase heat transfer in TPCTs to facilitate the nucleate pool boiling heat transfer coefficient calculations for thermosyphon users. This paper can be taken as a starting point in the study of pool boiling in thermosyphons and heat pipes.

Large amounts of heat are rejected by hot steel when it is cooling during the manufacturing process. In an earlier investigation a flat heat pipe (FHP) was constructed and tested in a factory for recovering this heat loss from steel wires by radiation and convection. In this paper, the performance of the FHP was examined by testing it at different configurations. In parallel a theoretical study was conducted. The FHP consisted of 14 stainless steel tubes connected by a bottom collector and a shell and tube condenser top header. The heat transfer area was increased by attaching a stainless steel at the back of the tubes. The effect of the back panel on heat recovery was examined by testing the FHP with the back panel and without it. In addition, the effects of the emissivity and absorptivity of the FHP surface on the thermal performance were investigated by testing the FHP both painted with high temperature black paint and with it unpainted. A theoretical modelling tool based on thermal network modelling was built. The theoretical prediction of the thermal performance of the FHP represented by the amount of heat recovery was compared with the experimental findings. The results of the FHP thermal performance were compared for four cases. The results indicated that heat recovery was greatly increased by painting the surface with thermal black paint. Furthermore, the back panel has a significant influence on the magnitude of heat recovery.

In this review, the operation and functionality of batteries used in industrial applications will be investigated. It will be discussed how and why batteries degrade and lose efficiency because of improper thermal management and based on that it will be explained what methods and techniques can be applied to reduce this impact. Through this, it will be explained how heat management methods could be used to thermally control batteries. In addition to this, it will be indicated what technologies can be employed to manage thermal boundaries of batteries. A comprehensive review of the current state of the art technologies currently used will be followed by that which will include how these technologies can be applied as thermal management systems for batteries.

Industrial waste heat is the energy that is generated in industrial processes which is not put into any practical use and is lost, wasted and dumped into the environment. Recovering the waste heat can be conducted through various waste heat recovery technologies to provide valuable energy sources and reduce the overall energy consumption. In this paper, a comprehensive review is made of waste heat recovery methodologies and state of the art technologies used for industrial processes. By considering the heat recovery opportunities for energy optimisation in the steel and iron, food, and ceramic industries, a revision of the current practices and procedures is assessed. The research is conducted on the operation and performance of the commonly used technologies such as recuperators, regenerators, including furnace regenerators and rotary regenerators or heat wheels, passive air preheaters, regenerative and recuperative burners, plate heat exchangers and economisers and units such as waste heat boilers and run around coil (RAC). Techniques are considered such as direct contact condensation recovery, indirect contact condensation recovery, transport membrane condensation and the use of units such as heat pumps, heat recovery steam generators (HRSGs), heat pipe systems, Organic Rankine cycles, including the Kalina cycle, that recover and exchange waste heat with potential energy content. Furthermore, the uses of new emerging technologies for direct heat to power conversion such as thermoelectric, piezoelectric, thermionic, and thermo photo voltaic (TPV) power generation techniques are also explored and reviewed. In this regard, the functionality of all technologies and usage of each technique with respect to their advantages and disadvantages is evaluated and described.

This paper investigates the application of heat-pipe based heat exchanger for improving the energy efficiency of industrial processes. In particular, the case of the ceramic industry is addressed and the potential heat recovery and reduction of fuel consumption is determined. A theoretical model is constructed based on the established, proven performance characteristics of heat-pipe technologies and the performance of the ceramic process are calculated using numerical simulation. The results of the kiln numerical model are then combined to the theoretical model of the heat-pipe based heat exchanger and the heat recovery potential is evaluated as well as the reduction of fuel consumption. The combined theoretical and numerical approach demonstrates that the application of the heat pipes based heat exchanger to the cooling stack of the ceramic kiln enables to recover more than 863 MWh of thermal energy that can be used for heating up the hot air stream of the pre-kiln dryer. Thus, approximately 110,600 Sm-3 per year of natural gas can be saved from the burners powering the dryer and the emission of 164 tonnes per year of carbon dioxide can be avoided. Additionally, the avoided cost due to the fuel consumption reduction amounts to more than 22,000 Euro per year. These figures support the application of the heat pipes based heat recovery to the ceramic process from the viewpoint of the improvement the energy efficiency and environmental impact and also of the economic investment. (C) 2018 The Authors. Published by Elsevier Ltd.

European Union’s Horizon 2020 research and innovation programme under grant agreement No. 680599.

Management in energija odpadkov : 10. mednarodna konferenca o trajnostni energiji in varstvu okolja. Deseta mednarodna konferenca o trajnostni energiji in varstvu okolja - SEEP 2017 je bila organizirana od 27. do 30. junija 2017 v Bledu, in sicer Fakulteta za kemijo in kemijsko tehnologijo Univerze v Mariboru, Slovenija, in Univerza za zahod Škotske. Cilj SEEP2017 je združiti raziskave na področju trajnostne energije in varstva okolja z vsega sveta. Prispevani prispevki so združeni v 18 sej, da bi bralcem zagotovili dostop do 300 prispevkov avtorjev iz 52 državam. Zahvaljujemo se uglednim plenarnim in osrednjim govornikom ter predsednikom, ki so prijazno privolili v sodelovanje na tej konferenci. Prav tako smo hvaležni vsem avtorjem za članke in člane komisije. Menimo, da znanstveni rezultati in strokovne razprave ne bodo le spodbuda za razvoj, temveč tudi za ustvarjanje novih prijateljstev in morebitnih prihodnjih znanstvenih razvojnih projektov.

The majority of the energy demand in industrial application is primarily used for heating purposes. Recovering waste heat could contribute to significant reduction of production cost and greenhouse gas emission. In this paper, an innovative heat recovery system was designed, manufactured and tested. The Flat Heat Pipe (FHP) is designed to recover the heat by radiation from hot steel rods during the manufacturing cooling process. The FHP system is composed of stainless steel heat pipes linked by a collector at the bottom and a shell and tube top header. The thermal performance of the FHP was investigated by testing the system at two positions from the barrier of the wires conveyor. The amount of the energy recovered and the working temperature of the FHP is also reported. The experimental results show that the heat transfer capability of the FHP is strongly influenced by the hot source temperature. It was observed from the results that the FHP is an innovative technology for waste heat recovery from industrial applications with high efficiency.

Heat pipes are becoming increasingly popular as passive heat transfer technologies due to their high efficiency. This paper provides a comprehensive review of the state-of-the-art applications, materials and performance of current heat pipe devices. The paper is divided into four main parts; low temperature heat pipes, high temperature heat pipes, thermal modelling of heat pipes and discussion. The low and high temperature sections present an extended list with suitable working fluids and operating temperatures, along with their compatibility with casing materials. Furthermore, the sections focus on some of the most widespread industrial applications, such as solar, nanoparticles, Rankine cycles, nuclear, thermoelectric modules and ceramics, in which heat pipe technologies offer many key advantages over conventional practises. The third part of the paper consists of a thorough analysis of the thermal modelling side of heat pipes. Internal and external thermal modelling techniques, theories and methodologies are presented in this section, for various applications such as non-Newtonian fluids, nano-fluids, solar, geothermal, automotive, hybrid storage and nuclear systems. The final part of the paper discusses the limitations of heat pipes and the reasons why they are not implemented in more aspects of our lives. Operational limitations, cost concerns and the lack of detailed theoretical and simulation analysis of heat pipes are some of the point covered in this section. Finally, some of the recent and future developments in the field are discussed.