• Energy Research

Heat exchangers are utilised in many heating and cooling processes within different industries. The effectiveness of the heat exchanger is partly dependent on the flow and heat transfer characteristics of the fluid inside the heat exchangers. This study focus on analysing the flow and heat transfer characteristics of water within a straight circular pipe with twisted-tape inserts. For this study, a 3D numerical model for straight circular pipe 11.08 mm diameter and 1920 mm length was developed with water as the heat transfer fluid and validated using published experimental data. The simulation was done for a range of Reynolds numbers (1500–24,000) and four twisted-tape inserts with different widths (1, 2, 2.5 and 3 mm). The results revealed that the twisted-tape inserts induced noticeable swirling of the flow inside the pipe. The swirling was more prominent with the wider twisted-tape geometry (1 mm × 3 mm). The pressure drop along the pipe also increased with the use of the inserts. The numerical results also gave significant improvement in the heat transfer with the use of the twisted-tape inserts. The enhancements achieved with the twisted-tape inserts was between 23% and 29% with higher enhancement achieved with the wider twisted-tape inserts.

There is a need to change business and behaviour models from the linear to the circular in order to conserve energy and resources. This paper identifies what pro-circular behaviours can influence the development of a Circular Economy, with particular reference to the retail refrigeration industry. Pro-circular behaviour is an action that is brought about due to the prioritisation of resource-efficiency with the aim of supporting the growth of a Circular Economy. A Circular Economy is an economic and industrial system where resources are kept in use for as long as possible. Greater uptake of alternative business models in the UK could help to create a more sustainable industry in retail refrigeration.

Refrigeration has become an essential part of the food chain. It is used in all stages of the chain, from food processing, to distribution, retail and final consumption in the home. The food industry employs both chilling and freezing processes where the food is cooled from ambient to temperatures above 0°C in the former and between -18°C and -35°C in the latter to slow the physical, microbiological and chemical activities that cause deterioration in foods. In these processes mechanical refrigeration technologies are invariably employed that contribute significantly to the environmental impacts of the food sector both through direct and indirect greenhouse gas emissions. To reduce these emissions, research and development worldwide is aimed at both improving the performance of conventional systems and the development of new refrigeration technologies of potentially much lower environmental impacts. This paper provides a brief review of both current state of the art technologies and emerging refrigeration technologies that have the potential to reduce the environmental impacts of refrigeration in the food industry. The paper also highlights research and development needs to accelerate the development and adoption of these technologies by the food sector.

This paper presents the simulation of a low-temperature gas-fired ammonia-water absorption chiller for refrigeration applications. The model was developed as part of a research effort to investigate microturbine-based tri-generation systems for application in the food retail industry. The absorption chiller model was developed in the TRNSYS environment by integrating the main component models in the system and will form part of an overall TRNSYS-based supermarket model. The chiller model was validated against experimental results obtained on a 12 kW absorption chiller in the laboratory. The model was subsequently used to investigate the influence of important design and operating parameters on the performance of the chiller. © The Author 2009. Published by Oxford University Press. All rights reserved.

Chilled foods have been available since the 1960s. However, over the past 20 years, the market has been driven by the huge social, economic and demographic changes that have influenced our eating habits. This has contributed to making the chilled food production and retail in the UK one of the world’s fastest-growing food sectors with food retail stores, restaurants and cafeterias. One very important fixture in these commercial establishments is the display cabinet where food is chilled and displayed. Many guidelines & regulations exist regarding displaying of food in cabinets. Amongst these are ones that relate to food deterioration such as the Food Hygiene Regulations 1995 (updated in January 2006), which related specifically to the retail sale and distribution of chilled foods. The most important point of these regulations was a requirement for sensitive foodstuffs to be maintaining at 8°C or below (Part II). These regulations were focused on reducing the risk of bacterial spoilage associated with chilled foods. The Regulations did not engage in the deterioration problems associated with moisture transfer and evaporating loss of unwrapped chilled foods displayed in delicatessen cabinets. This paper present result from theoretical and experimental investigation into the display shelf life in terms of bacterial spoilage and weight loss for some unwrapped sandwiches components including vegetables, tuna, cheese and beef. The output of this work showed that the display shelf life in terms of weight loss is shorter compared to the shelf life in terms of bacterial spoilage and it’s related to food drying rate. Surface drying, increases the weight loss and leads to colour changes that are undesirable and results in shorter display shelf life. Weight loss was affected by air relative humidity, velocity and temperature. Therefore, more consideration should be given to environmental boundary conditions, which have direct impact on the quality and shelf life of unwrapped product.

This paper shows the results of a novel research conducted with the overall aim of developing a system that can provide continuous desalination. Productivity enhancement of solar stills is regarded as the main purpose of the investigators in desalination field. This paper represents the experimental results in a new approach of paraffin + graphene oxide nanoparticles mixture. The paraffin mixture in a semicircular, triangular and rectangular absorber with paraffin +graphene oxide of 0.1, 0.3 and 0.5 wt% has been investigated. The finding indicated that for all absorbers, the use of paraffin + graphene oxide in higher weight fractions enhances daily freshwater production. The results showed that the thermal performances are greater applying graphene oxide + paraffin of 0.5%wt with semicircular absorber compared to triangular and rectangular absorber. The achievement of the present paper can be implemented to design more efficient absorbers for solar still parts.

This paper presents a feasibility study of the technical and economic viability of introducing combined heating and cooling networks in London, referred to collectively in this paper as “thermal networks”. The study begins with a review of the current and potential future demographic and energy trends for London. This is followed with detailed energy analysis of three different thermal network configurations to identify the most viable thermal network configuration for London. Future projection analysis was also carried based on a number of potential building mix scenarios. The study revealed that by using thermal network with heat recovery produced significant energy savings and subsequent carbon savings by upto 56%. The majority of the energy saving and equivalent CO⁠2 emission savings resulted from the reduction of the heating energy required to cater for the loads due the viability of heat recovery from the cooling network into the return of the heating network. The study also revealed that by utilising thermal networks, with central energy centre approximately 1831 tonnes of CO⁠2 equivalent could be saved per annum compared to traditional supply methods. With a minimum assumed system life of 25 years this equates to approximately 46,000 tonnes CO⁠2.

© 2016 Elsevier Ltd. All rights reserved.Pulsating or otherwise known as oscillating heat pipes (OHPs) are two-phase heat transfer devices that can offer simple and reliable operation (no moving parts and vibration-free) with high effective results. This paper presents findings from an experimental flow visualization study into the various types of flow patterns within a closed-loop OHP with Fe2O3/kerosene as the working fluid. The complete transitions from nucleate boiling to formation of liquid slug and vapour plug were observed in the closed-loop OHP. From the flow visualization results, it was deduce that the motions of liquid slugs and vapour plugs are complex and influenced by many factors, such as heat rate, filling ratio and tube diameter. The findings also revealed that bubble generation and bubble growth induced a large driving force which contributed to the random motion of liquid slugs and vapour plugs. The flow visualization also revealed that bubbles with diameter equal to the inner diameter of the tube, otherwise known as tube-size or TS bubbles, were generated when the velocity of liquid slug was lower or equal to 0.15 m/s and the velocity of the liquid-vapour interface increased as TS bubbles were generated.