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The dehydration of a tilapia fillet is conducive to its preservation. However, dehydration results in high energy consumption and quality variation. Ultrasound-assisted osmotic dehydration as a pre-treatment combines the advantages of strong permeability by preservatives and the cavitation effect and can improve the quality of tilapia fillets dried by heat-pump drying while decreasing the drying time and maintaining the quality of the dried products. The whiteness, texture, rehydration rate, Ca2+ adenosine triphosphate synthase (Ca2+-ATPase) activity and the comprehensive score were used as criteria in single-factor experiment son ultrasound power, ultrasonication and permeate concentration. Based on the results of the single-factor experiment, the Box-Behnken central composite design was adopted to achieve response-surface optimisation. The results indicated Ultrasound-assisted osmotic dehydration as a pre-treatment with suitable ultrasound parameters can significantly improve the quality of heat-pump dried tilapia fillets and provides references for optimising the drying process. [ABSTRACT FROM AUTHOR]

In this study, a small-scale test rig of CO2 transcritical power cycle (T-CO2) system driven by low-grade heat has been developed and investigated experimentally. The test rig consists of a number of essential components including a CO2 turboexpander with high speed generator, finned-tube air cooled condenser, liquid receiver, CO2 liquid pump and CO2 gas generator. The CO2 is heated in the plate-type gas generator by hot thermal oil flow which is circulated and heated by exhaust flue gases from an 80kWemicroturbine CHP unit. The test rig has been fully commissioned, instrumented, controlled and is ready to operate experiment as required. Subsequently, at constant heat sink (ambient) and heat source (thermal oil) temperatures, a series of experiments have been carried out to examine the effects of various important parameters on the T-CO2 system performance. These include thermal oil flow rate and CO2 mass flow rate etc. Preliminary experimental results show that the CO2 TPC is applicable for the low temperature heat sources to generate power although further efficiency improvements are needed. In addition, the experimental outcomes can instruct future optimal system design and controls. [ABSTRACT FROM AUTHOR]

Noticeable technological advances in transcritical R744 (or “CO2 only” or pure CO2) supermarket refrigeration systems have recently occurred. Consequently, the trend towards such technologies has been greatly intensifying, leading these solutions to take root in European commercial refrigeration sector.In this theoretical study, the performance of the present state-of-the-art pure CO2 refrigeration plants was extensively investigated for an average size food retail located in various European climate contexts. The results revealed that, compared to a R404A direct expansion unit, the energy efficiency limit commonly experienced by transcritical R744 refrigerating systems with rise in outdoor temperature disappears with the aid of the multi-ejector concept. Furthermore, depending on the selected solution, the current advanced commercial “CO2 only” configurations feature energy savings ranging from 3% to 37.1% across Europe over a R404A unit. At last, this investigation demonstrates that transcritical R744 ejector supported parallel systems are the most highly efficient and climate friendly technologies for European food retail industry. Moreover, noteworthy energy conservations can also be related to the solution combining parallel (or auxiliary) compression and medium temperature (MT) overfed evaporators. [ABSTRACT FROM AUTHOR]

A significant amount of national energy in the UK has been consumed in the residential sector mainly for space heating and domestic hot water production. Currently, gas boilers are mostly applied in the domestic water heating which contribute significantly to excessive CO2emissions and consumption of primary energy resources. The issues can be solved by popularizing heat pump systems that are attributable to higher performance efficiency than those of traditional gas boilers. Even so, the heat pump system performance can be further enhanced and improved if the dissolved gases in its hot water circuit can be efficiently discharged. To achieve this target, the bubble behaviors in the heat pump water heating system need to be extensively investigated. Based on a purposely built test rig of an air-water heat pump system, the effects of various heat pump hot water side parameters on gas microbubble diameters were measured and analyzed through different experimental conditions. The operational parameters include water flow rate, water flow pressure, system heating load and water flow dissolved gas saturation ratio. It is found from the measurements that the hot water flow rate is the dominate parameter which affects the average bubble diameter and bubble number distribution at different bubble sizes. The research outcomes can significantly contribute to the understanding of gas bubble behaviors at domestic heat pump water heating systems and thus the efficient way for the discharging of the associated dissolved gases. [ABSTRACT FROM AUTHOR]

Integration of renewable energy with energy conversion application for hot water production is a significant technology to be studied for industrial, commercial and residential proposes. It has been further enhanced since the international energy agency (IEA) puts effort to standardize such kind of technology. In this paper, a novel study has been carried out experimentally to control an indirect solar assisted heat pump (IDX-SAHP) system integrated with a latent heat storage (PCM) tank. The PCM heat exchanger tank was designed specially and controlled automatically which allowed storing excess energy during the day and releasing it when needed. In addition, a system control strategy has been purposely designed and implemented in a Building Management System (BMS) to ensure the stable and reliable system operations. The experimental results show that the PCM heat exchanger tank installation has a significant effect on the system operation stability and can improve the COP of the IDX-SAHP system at different weather conditions and a specified hot water load profile. [ABSTRACT FROM AUTHOR]