Conference Agenda

Ultra-low temperature (ULT) freezers maintain storage temperatures of -50°C to -86°C in ambient conditions ranging from 16°C to 32°C. Freezers with cascade refrigeration systems have been used for decades to preserve cultures, vaccines, samples, specimens, and viruses. Typically, these ULT freezers are stand-alone units, and large institutions operate freezer farms containing hundreds of freezers. Climate change has contributed to an increase in average global temperatures and more frequent high-temperature extremes, such as heatwaves. This paper examined the impact of rising temperatures on ULT freezers. Three key changes were identified: a decrease in efficiency, an increase in heat load, and an increase in component operating temperatures. These changes were investigated using a 400-litre freezer, which maintained a storage temperature of -85°C at ambient temperatures of 20°C and 33°C. The evaluation included the power profile, the pressures for both stages, and the temperature in the compressor compartment.

Rising ambient temperatures significantly impact the thermodynamic performance of transcritical CO₂ refrigeration systems. To investigate these effects, detailed mathematical modelling of the gas cooler was developed and integrated into a CO₂ refrigeration system model. The thermodynamic performance was investigated in the broad range of ambient temperature between 25 ^oC and 40 ^oC, and high-side CO₂ pressure from 75 bar to 140 bar. The results of COP and cooling capacity show a significant decrease with increasing ambient temperature. To improve the performance of CO₂ refrigeration systems at high ambient temperatures evaporative or spray cooling can be employed to enhance the heat transfer in the gas cooler and reduce gas cooler temperature and pressure. In this paper experimental and modelling results are used to investigate the impact of spray cooling on the performance of CO₂ refrigeration systems at high ambient temperatures.

As global temperatures rise due to climate change, convenience stores face increasing challenges in maintaining optimal refrigeration and store temperatures. This study evaluates the impact of extreme heat on a small independent UK convenience store using an EnergyPlus™ model to simulate thermal dynamics during the UK July 2022 heatwave. The analysis examines air conditioning (A/C) performance, refrigeration efficiency, and indoor temperature stability under varying cooling capacities. Results show that if the A/C system was designed using EnergyPlus™ algorithms, there would be sufficient spare capacity, with the model predicting that the store temperature would stay stable even during outdoor peaks of 40.15°C. Sizing for a peak outdoor temperature of 27.7°C revealed that indoor temperatures exceeded the setpoint by 4.0°C. To enhance store resilience, strategies such as A/C sizing for higher peak temperatures are advised to adapt for future climate conditions.

While refrigeration and air conditioning bring relief during heatwaves, the resulting direct greenhouse gas (GHG) emissions from refrigerants and indirect emissions from energy consumption further contribute to global warming, creating the vicious cycle of cooling. This study, developed under Germany’s International Climate Initiative (IKI), introduces comprehensive scenario modelling to analyse an outlook based on diverse sustainable cooling pathways of the GHG emissions in the Middle East and North Africa region and Türkiye as basis to inform policymaking. Expert interviews were conducted with stakeholders from Egypt, Jordan and Lebanon to provide an overview of the impact of sustainable cooling policies and establish a baseline reflecting the current cooling landscape in the respective countries. The study finds that without policy interventions, each of the countries is positioned to face a significant rise in electricity consumption due to continued reliance on conventional technologies. Based on the scenarios modelling, this study provides policy recommendations.

Refrigeration plays crucial role in preserving perishable food items in millions of households. Its widespread use contributes significantly to electricity consumption and carbon emissions. According to Bureau of Energy Efficiency, refrigeration sector consumed 67 TWh of electricity and generated 57 MtCO2 emissions in 2017. In 2022, domestic refrigerators consume 3 TWh of electricity. According to ICAP, domestic refrigerator sales are expected to increase by 1.7 times, while the commercial refrigeration sector is poised for a 2-fold growth, leading to a surge in energy consumption. However, energy efficiency policy initiatives aim to mitigate this trend, with projected savings of 38.8 TWh of electricity and 30.4 MtCO2 emissions by 2030.

This paper examines effectiveness of India's energy efficiency policies for domestic and commercial refrigerators, implemented since 2006, and socio-economic benefits of using energy-efficient refrigerators. It sheds light on journey, achievements, and prospects for doubling energy efficiency and sustainability in the refrigeration sector.

This paper presents the findings of several works projecting global trends in population growth, human development index (HDI) and climate change along five Shared Socioeconomic Pathways (SSPs), and how these separate disciplines impact the demand for refrigerated services. A methodology for approximating a country’s refrigerated storage capacity from the HDI value has been developed and presented in this paper. A globally applicable R-744 refrigeration system was simulated and used as a benchmark to approximate the global energy consumption required to support the evolving demand on refrigeration storage capacity throughout the 21^st century. An assessment of the solar energy potential from the expanding refrigeration storage capacity has been discussed and presented, highlighting an opportunity to offset the sector’s energy consumption and by extension, support the global transition to Net Zero society. The finding of this paper will provide global to national insight on how refrigeration storage will change by the end of the century for the benefit of cold chain strategies.

This paper presents a case study on the total replacement of an aging ammonia pumped circulation system supplying a cold and chill storage warehouse facility using multiple low charge modular packaged ammonia refrigeration systems in Scotland. Installation and commissioning took place across 2020-2021 with the package units replacing the plant room style system which had been operational since 1979.

This paper gives a design overview of the new plant and summarises the benefits of the external package unit type system over the original pumped circulation system with insight into the challenges faced implementing change on an aging site. This study will also analyse store temperature performance and energy usage across a 12-month period with comparison to historical site data.

At the same time climate-driven national policies are requiring increased uptake of heat pumps. Current refrigerants include HFCs that exhibit significant warming impact when emitted, thus accentuating the climate impact. Use of negligible-GWP hydrocarbon (HC) refrigerants can help mitigate this impact. The present work is a detailed assessment considering technical, economic, environmental and safety implications, all of which are interrelated to some extent. Differences in materials and other inputs are used to determine implications of cost, equipment size and lifetime carbon dioxide equivalent (CO₂e) emissions. Overall, significant benefits for emissions reduction are seen when switching from R410A (or from R32) to HCs. Thus, domestic heating and air conditioning, considering higher temperatures and decarbonisation targets, can be applied without adverse contributions to climate change or equipment cost.

The performance of the refrigeration plant is directly affected by the surrounding temperature and humidity. The heatwave in 2022 saw temperatures in some parts of the UK exceed 40°C for the first time. Climate models predict peak temperatures exceeding 40°C regularly in the near future. The integrity of the cold chain rests upon proper functioning of refrigeration equipment. Although forward thinking designers are considering higher ambient temperatures, there is no standard or operating guidelines to steer industry in the right direction.

This study carried out surveys and audits to investigate the preparedness of the cold chain to warmer ambient temperatures. Cold stores tend to have older plant (mean of 10.9 years) compared to retail (4.6 years). Condensing temperatures were often higher than optimum, with an example of 40°C recorded when the ambient was only 15°C.

This study recommends a standard method for choosing design ambient temperature, considering location in the UK and life of equipment.

The integration of microchannel heat exchangers (MCHEs) with phase change materials (PCMs) presents a promising approach for improving energy efficiency and thermal management in space heating systems. These are attributed to their high surface area-to-volume ratio, compact design, faster PCM charging, and higher energy density. Correspondingly, a purpose-designed MCHE was fabricated, utilizing airflow as the heat transfer fluid (HTF), and incorporating organic PCM A27 within microchannels. A series of experiments were carried out to study the thermal performance of the MCHE throughout PCM charging and discharging processes at different operating conditions. Furthermore, a validated computational fluid dynamics (CFD) model was developed to optimize the thermal storage performance at various operating and design conditions. The integration of advanced heat exchangers with energy-efficient thermal storage materials holds significant potential to enhance building heating technologies, offering improved energy efficiency, faster thermal response, and greater sustainability.

Refrigeration cycles operating below −50 °C are highly inefficient and rely on refrigerants with high global warming potential. This inefficiency is primarily due to limited technological advancements and a lack of comprehensive studies on suitable refrigerants for ultra-low temperatures. To address this gap, this article aims to analyze the experimental behaviour of a cascade compression cycle for ultra-low temperature refrigeration. The refrigerants analysed are R290 in the high-temperature stage and R170 in the low-temperature stage. These refrigerants have been compared with the R404A/R23 pair, which is commonly used in the sector, and the R448A/R170 pair. The results indicate that the R290/R170 pair provides superior performance in terms of the coefficient of performance. A Total Equivalent Warming Impact analysis demonstrates its environmental advantages. It also achieves the best results in compressor volumetric efficiency and discharge temperature.

Containerised refrigeration systems are designed to operate across a broad ambient temperature spectrum ranging from as low as -30 °C to as high as 50 °C in accordance with design requirements of ISO1496-2:2018. Whilst the majority of shipments are at well within this range, operation at 50 °C in container holds is relatively common. Vessels holds are cooled either by ambient air or seawater. With tens or hundreds of 40’ containers, each with their own refrigeration system, operating in the holds, temperatures of 50°C and above are easily achieved.

The HFC refrigerants currently used by the marine industry, HFC-134a and HFC-404A, operate somewhat differently once the temperature goes beyond the design specification. A marine CO2 system is offered by one manufacturer therefore CO2 operation shall also be discussed.

It is found that operation in high ambients – even beyond 50 °C - is possible however it comes with coefficient of performance (CoP) losses.

This paper explores the challenges of selecting appropriate ambient temperatures in the context of rising global temperatures and analyses the impact on plant performance. The first section examines whether planning for worst-case temperature scenarios is the most effective approach, considering regional variations and future climate projections. The second section investigates plant performance in high ambient temperatures, using real-world data from cold chain facilities and comparing it with theoretical predictions.

By reviewing electrical consumption, store temperatures, plant operational conditions and coefficient of performance, the paper identifies deviations between predicted theoretical and actual performance in three key locations including the South West, Midlands, and Scotland. This analysis offers insights into temperature management, energy consumption, and the implications of high ambient temperatures on plant efficiency.

Climate change and the associated temperature rising obliges cold chain to work under more adverse conditions, increasing the risk related to malfunctions or failures of refrigeration apparatus and systems, especially those corresponding to commercial refrigeration, where plug-in cabinets are often used. To reduce failure risk, automated fault detection and diagnosis methods represent a very interesting approach as malfunctions can be immediately detected or even prevented. However, such methods were historically based on large amount (high frequency) of data produced by multiple sensors that are often difficult to install in real commercial refrigeration systems. The current paper presents an automated fault detection and diagnosis system based on artificial intelligence (AI) algorithms that is specifically designed to be incorporated into low-cost internet of things (IoT) temperature controller devices. Those IoT controllers involve limited temperature sensors and low data register frequency. The purpose of the system is to detect and prevent common commercial refrigeration apparatus faults without increasing typical installation complexity.

This study examines the current energy use across sectors and segments of the Norwegian onshore seafood industry, with a focus on farmed fish, as well as pelagic, shrimp and whitefish from capture fisheries. Data on specific energy consumption, production, and exports were collected from open sources, reports, industry communications and site inspections. Extrapolation methods were applied to estimate the overall energy use across the subsectors. The findings reveal a significant dependency on fossil fuels in some sectors. Thermal processes, including refrigeration and heating, are the largest contributors to energy consumption, making these systems a priority for energy efficiency strategies. Rising temperatures, particularly of seawater, could have significant implications not only for marine life but also for the performance of thermal energy systems. Implementing energy efficiency measures is crucial for adaptation, and this work identifies and describes several such measures tailored to the seafood industry.

The rising global temperatures associated with global warming enforce to reduce the emissions from heating and cooling systems. Conventionally, the refrigeration and space heating demand of a supermarket is catered by the refrigeration system and the natural gas fired/electric boiler, respectively. The environmental and economic advantage of replacing these systems with a conventional booster CO₂ refrigeration system with heat recovery and an integrated heat pump (CB_HP) were analysed in this study. The variation in ambient temperature, electricity price, heat selling price and heating and refrigeration demand of the supermarket on a cold day in Stockholm (Sweden) were considered for the analysis. The results show that the total emissions and operating cost could be reduced by 94 % and 91 % as the conventional systems were replaced by CB_HP, respectively. Furthermore, the optimization of the economic performance of CB_HP for varying gas cooler pressure and temperature is carried out.

The effect of climate change on cold storage facilities will be evident in several different ways, including increased heat load on the plant, reduced capacity of the refrigeration system, impaired efficiency, higher energy costs and increased business risk resulting from all of the above. If the plant is already old and in a poor state of repair the additional stresses on operation could be substantial. Modifying older plant to account for these factors can increase the risk of premature failure. The business risk can be mitigated by adding refrigerating capacity modules to the facility without making any changes to the existing system and without sinking significant additional capital into an aged plant. This paper presents the factors to be considered when contemplating this type of problem and provides a case study of a beneficial project which enabled a cold store operator to spread the capital requirement over several years while gaining the benefits of improved reliability and reduced energy costs.

The most common method of defrosting ammonia evaporators in large cold store or freezer systems uses hot gas. There are several methods of achieving an effective defrost but they can cause a significant penalty in system capacity and operating cost if they are not maintained in good condition. This paper describes the options for hot gas defrost and outlines the steps required to maintain good performance, with the consequences of failure to do so. Design guidance to eliminate the problems for the construction of new systems is provided and maintenance checks are described.

The international standard for frozen foods is -18°C (0°F). The "Three-Degrees-of change" initiative proposes to explore the interest of raising from -18°C to -15°C the frozen storage temperature in order to save energy. The analysis on the impact of this initiative on the quality of frozen foods shows that a 30% loss in shelf life is expected for food stored at -15°C compared to -18°C (Le-Bail et al., 2025). A focus is proposed in this study on the impact of temperature oscillation during storage; indeed, in the case of foods with a lower initial freezing point (ie IFP of -5°C vs -1°C), a same temperature oscillation will result in a larger change in LOF and a_w. Therefore, the shelf life is likely to be more affected in a food with a lower IFP.

Fresh food (meat, dairy products…) needs to be kept between 0 and 8°C during transport and storage in a cold chain by refrigeration systems and suitable packaging. In this work, we focus on secondary packaging, which is used to transport products from production to the point of sale. EPS (Expanded Polystyrene) boxes are often used because of their thermal efficacy, low weight, and cost. However, because of its large volume and low density, EPS is difficult to recycle in many countries. Cardboard is an alternative to EPS and numerous studies have shown its potential from an environmental point of view or based on its thermal performance. Using an experimentally validated thermal model, different designs of cardboard packaging with modified air spaces or corners are tested. Our objective is to find a design that can withstand high temperatures for a certain duration.

Rising global temperatures are straining refrigeration systems, increasing cooling loads, reducing efficiency, and amplifying peak electricity demand. Thermal Energy Storage (TES) offers a cost-effective, scalable solution by shifting refrigeration loads, enhancing efficiency, and improving grid flexibility. Unlike batteries, TES has a longer lifespan, requires less maintenance, and eliminates fire risk, making it an ideal demand-side resource.

This paper explores TES as a climate adaptation tool, demonstrating its ability to shift cooling demand, reduce peak loads, and enhance grid resilience. TES enables long-term energy storage without degradation, providing refrigeration industries with a sustainable, cost-effective alternative amid intensifying climate challenges. As utilities and policymakers prioritize grid-stabilizing solutions, TES emerges as a proven strategy for resilience, operational efficiency, and decarbonization.

Keywords: Thermal Energy Storage, Refrigeration Energy Management, Peak Load Shifting, Demand Response, Grid Resilience, Decarbonization

This work experimentally assesses R472B as a lower-GWP alternative to R23 in a two-stage cascade ultra-low temperature refrigeration system. First, the pull-down performance from 15, 20 and 25 °C down to –70 °C is analysed. Then, the hysteresis operation with set freezer temperatures of –70, –60, and –50 °C is studied. The pull-down time was higher for R472B compared to R23, with a time difference from 23 to 40 minutes. Regarding the hysteresis operation, the lowest energy consumption for all the tested conditions was achieved by R472B, being 8.4 to 17.5% lower than R23. The cooling capacity of R472B was 9.4 to 26% lower at –70 and –60 °C, and up to 13% higher at –50 °C. COP was comparable at –70 and –60 °C, and at –50 °C, R472B COP was up to 15.6% higher. The environmental analysis of the hysteresis operation shows that equivalent CO₂ emissions can be reduced by 65% when using R472B instead of R23.

The advantage of the diffusion absorption refrigerators (DAR) is that they can be thermally driven by waste heat or solar energy, without electricity consumption. This allows cooling at low carbon footprint, reduced to the embodied energy and carbon dioxide at the production, maintenance and recycling of the installations. For the solar cooling, the heat required for boiling and movement of the binary solution in DAR, is obtained by converting the solar energy in solar collectors. The change of the solar irradiation during the day is resulting in a variable power input in the generator and subsequent changeable cooling capacity of DAR. An experimental analysis of a laboratory DAR at variable heat supply was carried out to analyze the limits of these changes. The variation of the cooling capacity and the coefficient of performance of the refrigerator with the energy input have been established. On this basis, the possibilities for cooling by a DAR based solar system in Sofia were investigated.

This work proposes an experimental assessment of R448A as a lower-GWP alternative to R404A in the high-temperature stage of a R404A/R23 ULT two-stage cascade refrigeration system. Furthermore, the use of capillary tubes and electronic expansion valves is compared. First, the pull-down performance starting from three ambient temperatures (15, 20, and 25 °C) down to –80 °C is analysed. Then, the hysteresis operation with set freezer temperatures of –80, –70, –60, and –50 °C is studied. The pull-down time was higher (38 to 55 min slower) using the capillary tubes compared to the electronic expansion valves. Also, the energy consumption of the hysteresis operation was higher (up to 32.3% higher) using the capillary tubes. A comparable energy consumption and cooling capacity were obtained with R404A/R23 and R448A/R23 using the electronic expansion valves. The highest COP was achieved by R448A/R23 (up to 10.2% higher than R404A/R23). Therefore, the suitability of R448A as a replacement for R404A in ULT refrigeration is confirmed.

Given the coming prohibition of fossil fuel boilers in different sectors, the study assesses the viability of industrial heat pumps connected to district heating and cooling networks. It compares it with evaporation connection to ambient in six Italian cities, focusing on the potential for energy savings and reduced environmental impact. Italy's diverse climatic conditions significantly influence the performance of heat pumps, which are highly dependent on local temperatures. This paper highlights the advantages and limitations of adopting heat pumps for 75 °C heating production. The findings reveal significant energy-saving potential and alignment with sustainability goals in suitable district heating configurations and favorable climatic conditions. However, limitations emerge in less optimal environments, where alternative strategies may be required to maintain efficiency. This work provides valuable insights into the role of industrial heat pumps in smart city applications, offering guidance for their adoption in Italy and other regions with comparable climates.

With global warming predicted to reach dangerous levels, action must be taken to increase the operating efficiency of refrigeration plants in both new designs and existing installations. Many existing plants have been designed with higher cooling densities than they actually require and so fixed speed screw compressors run at part load with poor efficiencies.

This paper is a case study of a refrigerated distribution centre that sees one of the installed 2.2MW duty fixed speed screw-compressors running at reduced capacity for long periods of time during lower ambient temperature conditions. To improve plant efficiency during these low-load conditions the 2.2MW compressor was swapped out with a reduced capacity VSD driven compressor.

This paper assess the plants historical energy usage data and uses compressor selection software to predict the energy savings of this retrofit.

According to sustainability targets, the refrigeration and heat pump sector is switching to low Global Warming Potential (GWP) working fluids. Due to this change, coefficient of performance (COP) of vapour compression system degrades. Thermoelectric sub-cooling method is one of the state of art idea to introduce vapour compression systems to improve coefficient of performance (COP) of the system. Nevertheless, the finding optimum operation point in dynamic operation is challenging especially at extremely high temperatures. Thus, main aim of this paper to investigate the proposed thermoelectric sub-cooler (TESC) design performance and create mapping to find optimum operation in low-charge propane system. The TESCs integrated downstream of condenser in an 8-kW propane heat pump test rig and experiments carried out for operating conditions where propane temperatures varied from 40°C to 50°C, auxiliary water stream relative temperature to the R290 was from -10°C to 10°C and thermoelectric modules voltage was up to 10.0 V DC.

The phase-out of high-impact refrigerants drives the adoption of low-GWP alternatives, with zeotropic mixtures emerging as promising candidates. However, their adoption introduces new challenges in adapting existing heat pump systems to maintain performance. This study evaluates the thermal performance of near-azeotropic R410A, and low-GWP zeotropic blends R454C, and R455A in a 4-kW indoor heat pump unit using a validated finned-tube heat exchanger simulation for cooling and heating modes. The results show that R455A and R454C exhibit significantly lower HTCs compared to R410A—61.4% and 49.5% in cooling mode, and 84.6% and 64.2% in heating mode, respectively—due to thermophysical property differences, reduced mass flux, and large glide temperature differences (GTD), which cause a cross-parallel flow effect. To mitigate performance losses, circuitry optimization is highlighted as essential. This study emphasizes the need for careful system adaptation to ensure effective integration of low-GWP refrigerants in heat pump applications.

This paper shows the energy behavior of a chest-freezer of 7ft³ when is tested in different conditions of temperature and humidity which correspond of three geographical zones in Mexico: north, center and south. The refrigerant used is R516A which is evaluated like substitute of R134a which is the baseline refrigerant in the equipment. Results show an increase in the refrigerant mass of R516A respect to R134a in a 29.4%. Taking account of use of R516A, an increase in both COP as cooling capacity was found for climate conditions of center zone in comparison with north and south zones of 25.86% and 31.59% for the first parameter and 12.6% and 3.8% for the second. Finally, a reduction in specific compression work was got in the climate conditions of center zone being this of 15.3% and 29% respect to north and south zones.

Increasing temperatures lead to human mortality directly, by means of physiological response to extreme heat but also indirectly due to drought, flooding, famine, disease, wildfires, infrastructure disruption, conflict, etc. Numerous studies have attempted to quantify the mortality risk of the various individual consequences of climate change as well as the overall impact. Emissions of fluorinated refrigerants, as used in refrigeration, air conditioning and heat pump systems make a notable contribution to current and future warming and therefore some proportion of the overall mortality can be attributed to those refrigerants. Alternatives include hydrocarbons, which have negligible global warming potentials and provided they are correctly selected, can provide lower energy consumption. However, their higher flammability introduces an additional hazard which can also lead to fatalities. This study compares the climate-related mortality risk of HFCs with the flammability fatality risk of hydrocarbons in order to determine whether their adoption is can benefit society.

Meeting the increasing demand for cooling while reducing carbon emissions is critical for sustainable logistics in Norway’s fruit and vegetable supply chain. The Norwegian food market is dominated by three major retail chains, which manage their own distribution systems with the support of one main third-party import provider. Although parts of goods are transported by train, the majority relies on trucks, posing significant challenges for sustainability. Centralized storage systems coexist with local storage units for fruits and vegetables, leading to increased transport frequency and energy use. Transparency across supply chains is essential to optimize energy consumption, minimize food loss and waste, and lower CO₂ emissions. By improving cooling technologies, reform transport logistics, and integrating innovative sustainability practices, Norway’s food sector can address growing cooling demands while advancing toward reduced carbon footprints. This study explores opportunities to enhance the efficiency and environmental impact of cooling and transport systems in this context.

The ejector technology is one of the most promising solutions in vapour compression units, especially for natural refrigerant-based systems, i.e., the CO₂ refrigeration and mobile air-conditioning systems, due to the expansion work recovery, which extends the application of such systems. Nevertheless, the design of the two-phase ejector required complex capacity control, e.g., using several ejectors operated in single or parallel modes, a needle in the converging-diverging motive nozzle or the oscillator source. Therefore, the main aim of this paper is to evaluate experimentally the possible control of the two-phase ejector operation by implementing the thermoelectric sub-cooler. The experimental investigation was done using the test stand of the CO₂ ejector-based refrigeration system equipped with the prototype thermoelectric sub-cooler at different gas cooler outlet temperatures in the range from 25.0 °C to 45.0 °C determining different climate zones. The test campaign is defined to evaluate the potential of ejector capacity control providing the voltage of TEMs up to 10.0 V DC.

Traditionally, Cold TES (CTES) has been used in transport refrigeration in the form of eutectic plates mounted inside insulated boxes, especially for last-mile deliveries. Due to their flexibility, these boxes represent a valid option to increase the resilience of the cold chain under emergency situations, like floods, landslides, etc that are becoming more frequent.

To increase the overall sustainability of the entire solution, and to guarantee the accessibility to cheap and widespread refrigerants, this study presents and numerically evaluates the performance of an efficient cooling unit relying on an innovative TES configuration (eutectic tubes) and on natural refrigerant (propane), to replace a baseline cooling unit employing a synthetic refrigerant.

The numerical model is validated against experimental data measured on the baseline unit and demonstrates a +12.6% pulldown COP increase of the proposed system compared to baseline under standard test conditions. Considerations regarding propane charge are also included.

In the supply chain of fruits and vegetables, products are cooled down and stored in cold storage. However, they may be exposed to temperature fluctuations in the refrigeration system or when the cold product is summited to the warm ambient when the product is transported from one place to another. Water condensation can occur on the product surface. When the cold product is exposed to warm air, water condenses on the produce surface at temperatures below the dew point. Condensation on the product surface is an unfavorable condition for product quality. This promotes spore formation and the growth of microorganisms. This study aims to develop a model of heat and mass transfer in bulk fruits, including condensation. The model predicts air and product temperatures and water condensation within a container exposed to temperature fluctuations and was validated against experimental data. This model can potentially predict air and product temperature evolution and accumulation of water condensation.

Seafood plays an important role in the local food supply chain, especially in coastal areas of low- and middle-income countries (LMICs). Most small fishing vessels do not have an active refrigeration system to chill the catch, and only sometimes use ice brought from shore to chill the catch. The product temperature is known to have a major influence on product quality, and its control is therefore key to limit product degradation. Therefore, it could be advantageous to implement a CO₂ refrigeration system onboard. It helps control product temperature, preserves the quality and prevent spoilage of the catch. This paper presents experimental results of a compact subcritical CO₂ refrigerated seawater system (RSW). A Modelica model was developed to simulate the CO₂ refrigeration system's performance under various operating conditions. The simulation results suggest that using a capillary tube as an expansion device is a feasible alternative to manual expansion valves. However, further validation of the model is required to ensure performance reliability.

Abstract: Research and technological advancements in environmentally friendly refrigerants can effectively address the destruction of the ozone layer and mitigate global warming. An air compression system applied to residential air conditioning was proposed, using air as the work mass, the heating and cooling performance of the air compression system is theoretically analyzed to evaluate the system's overall efficiency. Conventional and ultra-low-energy buildings in Beijing, China, were studied and computationally analyzed using DeST and MATLAB tools to propose energy-efficient operation strategies. The simulation results demonstrate that the air compression system performs well in low-temperature heating and can meet the cooling and heating load demands of buildings. This study offers a theoretical foundation for the application of air compression systems in residential air conditioning.

Rising ambient temperatures and tightening decarbonisation targets are compelling the cold-chain sector to adopt self-sustained cooling units. This study develops a high-fidelity digital twin of an electric refrigerated van that integrates roof-mounted photovoltaic (PV) modules, a 10 kWh lithium-ion battery, and a -21 °C organic phase-change material (PCM) thermal buffer. The system is modelled in Modelica and dynamically driven by typical meteorological year data for Birmingham (UK). Simulation outputs are used to train Random-Forest regressors that predict battery state-of-charge (SoC) and compressor speed in real time. Results for a 12-h delivery mission show that adding 4 kg of PCM halves compressor cycling frequency and improves final SoC by 11 %, while solar charging recovers up to 18 % of daily refrigeration energy. The Random-Forest model attains an R² of 0.9990 for SoC and 0.9683 for rotor-speed prediction, enabling proactive energy management. The proposed architecture therefore offers a practical pathway to extend BEV range and resilience in food logistics.

In the UK the ten warmest years since 1884 have all occurred after 2002. Peak summer temperatures have been increasing with a peak of 40.3°C in 2022. Predictions are that temperatures will regularly exceed 40°C in the future. Currently not all refrigeration plant is able to cope with the high ambient temperatures being experienced. End users currently have to regularly reduce load to cope with the climatic conditions. This will only increase in the future with a greater need for short term and longer-term adaptation strategies.

This paper assesses how prepared the UK food industry is for these changes by assessing how exposed and vulnerable example poultry and milk chains are to climate change. The risk to these products is discussed and adaptation strategies suggested.

The strategy for tackling the challenges of high ambient temperatures in transcritical CO₂ refrigeration systems design must be innovative and multi-dimensional. In 2023 an innovative system featuring a pressure exchanger has been introduced in the market: it partially recovers the mechanical energy lost through the transcritical expansion valve to create additional free subcooling, while bolstering the performance and resilience of CO₂ refrigeration systems in hot climate. Together with other systems, this technology is tailored to reduce energy consumption year-round and ensure reliable operation under higher ambient temperatures. The present paper reports the ultimate experimental results of a pressure exchanger integrated in a real installation as part of a demonstration activity within the EU-funded ENOUGH project. The installation, located in Hungary, showed efficiency gain of 15% on average compared to standard booster systems, with temperatures higher than 20°C, and allowing a reliable and more efficient operation up to 45°C.

Extreme temperature conditions are becoming frequent also in temperate areas. While carbon dioxide is spreading all over the world, as a safe and environmentally friendly refrigerant, there is an increasing need for making CO2 cycle efficient also under high ambient temperature, while assuring affordability, serviceability and cost competitiveness.
The Plank transcritical cycle involves heat rejection at two different pressure levels: heat is first rejected at a pressure lower than the optimal one of corresponding simple cycle, thus resulting in reduced compression ratio, then pressure is increased by a pump, to meet the optimal rejection pressure as required by the secondary fluid thermal flow capacity.
In this paper, thermodynamic analysis of a CO2 refrigeration cycle identifies optimal heat rejection pressures under extreme ambient temperature. By numerical simulations the practical implementation of the cycle is critically discussed, considering finite heat rejection exchange areas. Considerations related to the relative sizing of the two gas coolers and comparison with simple compression cycle are presented.

Over the years typical refrigeration system design temperatures have risen from 28°C to 35°C. It is expected that peak temperatures in the future will regularly exceed 40°C. New refrigeration systems will need to be designed for the expected peak temperatures. Whilst refrigeration system energy efficiency may increase at times at peak temperatures, there is a great opportunity to use the peak temperature designs to improve energy efficiency all year round.

Forward thinking designers must navigate through issues of rising temperatures and the goal to achieve Net Zero by 2050. This paper aim is to focus on the design of new refrigeration equipment that will be in operation for decades to come. It will consider how improving the overall refrigeration system energy efficiency may help offset the rising peak temperatures.

In this work a novel technology to adapt transcritical R744 supermarket refrigeration systems to warm and hot climates as well as to rising temperatures was proposed and exhaustively investigated. The novel solution consisted of a booster device (increasing the transcritical fluid R744 pressure) followed by an air-cooled gas cooler and located between the conventional air-cooled condenser/gas cooler and high-pressure expansion valve. The results obtained revealed energy savings by from 2.31 % to 2.91 % in Seville (Spain) and from 4.64 % to 5.73 % in New Delhi (India). To further increase the energy benefits from the proposed technology, the use of an expander replacing the high-pressure expansion valve was also considered. As a consequence, energy savings by 7.80 % in Seville and 14.44 % in New Delhi with an additional investment recovery time of about 3 years in both of the selected locations were assessed.

Multiple industries require heat at a high temperature while dissipating heat at moderate to low temperature. In this context, sorption systems are a promising solution able to valorise waste energy at a low electricity cost, up to ten times less electrical power compared to an equivalent vapor compression heat pump. Specifically, Absorption Heat Transformer (AHT) are a type of absorption machine able to recover low-level waste heat () in order to provide higher-level heat (). In this study, a single stage AHT based on the NH₃/H₂O mixture is developed. Results enable to evaluate the performances of the AHT fed by industrial waste heat and cooled by ambient air and show that the standard architecture is limited by summer operating conditions. The influence of both the waste heat and ambient air temperatures are evaluated and the effect of the inclusion of a compressor in the cycle is discussed.

Hotels in India typically rely on synthetic refrigerant-based chillers for space cooling and diesel-fired water heaters for hot water production—both energy-intensive solutions that contribute significantly to global warming. Transitioning to natural refrigerants like CO₂ is a promising alternative, but this shift faces several challenges in India, including high ambient temperatures, limited technical expertise, resistance to adopting new technologies, and a shortage of skilled professionals. Demonstrating the real-world performance of such systems is essential to overcoming these barriers. This paper presents and discusses the first set of field data from a CO₂ heat pump recently implemented in a hotel located in a tropical region of India. The system successfully met its design goals, producing hot water at 80 °C while simultaneously providing chilled glycol-water at 2 °C. The results indicate that CO₂ based systems can effectively meet both heating and cooling demands in warmer climates, offering a sustainable alternative for the hospitality industry.

As global temperatures rise, the RACHP (refrigeration, air conditioning, and heat pump) sector faces unprecedented challenges in meeting cooling demands while minimizing environmental impact The increased reliance on cooling systems in Europe and worldwide intensifies greenhouse gas emissions, particularly through high Global Warming Potential (GWP) refrigerants.

This presentation will address the critical need for transitioning to low GWP refrigerants as a sustainable solution for the RACHP sector, focusing on technical and regulatory considerations. A shift to the ultra-low GWP refrigerant R-474A can significantly reduce the sector’s environmental footprint. While there are some technical challenges and market needs to be considered, the study will discuss the performance, safety, and availability of R-474A as ultra-low GWP refrigerant. Possibilities of retrofitting and adopting of new systems in different applications will conclude the presentation.

The urgency of climate change requires the adoption of alternative refrigerant with reduced GWP. R455A, a blend of R1234uf. R32 and CO2 met the sub-150 GWP requirement of EU-zone F-gas regulation and is considered for long-term alternative working fluid. For system design, pressure drop data is required, therefore, in this work the pressure drop is measured inside multiport mini-channel at different working condition with a newly assembled experimental system. Result shows an increase of pressure drop with mass flux and vapor quality. Data is compared against correlations of pressure drop in literature and a correlation is proposed with fitting experimental data for engineering purposes

Thermochemical storage based on the reversible solid-gas sorption process is a technical solution that can be relevantly applied in refrigeration, air conditioning and heat pump to meet the growing energy demand in buildings and industry. The “ThermoStore” process developed by Coldway© is a breakthrough innovation to accelerate the decarbonisation of industry. It allows for the valorisation of waste heat sources available in different temperature ranges or the storage of renewable energy. Such a process enables energy to be stored in the form of chemical potential with a high energy density, without losses and storage duration limitation, and provides simultaneous production of cold and heat. A demonstration of such a concept is currently being carried out as part of the Horizon 2020 project, MiniStor, “Thermal and electrical energy storage system for on-site residential installation”, that aims to provide both heating and cooling through an integrated, flexible unit exploiting low temperature solar energy (60 to 70 °C).