查看更多>>摘要：Tracking aggregation behaviour and changes in emulsifying properties of myofibrillar protein from mirror carp (Cyprinus carpio L.) induced by its oxidation during frozen storage under the effect of ice structuring protein were investigated. Solubility, net charge, emulsion properties of the sample without ice structuring protein decreased, meanwhile carbonyl, turbidity, the mean diameter in volume and the mean diameter in surface increased during frozen storage. As ice structuring protein addition increased, water-holding capacity and emulsifying properties of samples showed a trend of first increasing and then decreasing, while the tendency of oxidation and aggregation was opposite. Ice structuring protein of 2.0 (g/L) caused the most significant results (P < 0.05). Carbonyl, solubility and emulsion activity index of samples with 2.0 g/L ice structuring protein were decreased by 10.0%, 14.3% and 34.6% after 180 d, respectively. Results suggested that ice structuring protein could effectively prevent moisture loss from flesh, inhibit myofibrillar protein oxidation, and improve emulsion stability during frozen storage.
查看更多>>摘要：Aiming at the application of fruit and vegetables precooling, an innovative wet precooling system with ice slurry as a cooling medium was proposed. A small wet precooling room performance test platform was built. With apples as the precooling subject, the temperature and relative humidity in precooling room, the cooling rate and weight loss of apples as indexes, by changing the weight concentration of ice slurry additives (0%-8%), the ice fraction (0%-10%) and the ice slurry flow rate (50-150 L h-1), the precooling experiments were carried out. The results showed that increasing the concentration of ice slurry additives (NaCl) could effectively reduce the equilibrium temperature in precooling room. For the ice slurry solution with the additive concentrations of 0%, 2%, 4%, 6% and 8%, the equilibrium temperature in precooling room were 4.3 degrees C, 1.7 degrees C, 0.4 degrees C, 0.0 degrees C and -0.7 degrees C, respectively. When the ice fractions increased from 0% to 10%, the precooling time decreased from 165 min to 96 min, and the weight loss decreased from 2.11% to 0.42%. When the ice slurry flow rate increased, the relative humidity in precooling room increased, and the cooling rate of apples firstly increased rapidly and then leveled off. When the flow rate reached 100 L h-1, the relative humidity remained above 90%. The precooling system has a strong applicability, easy to realize the stable environment of low temperature and high relative humidity (0 degrees C, >90%), so it has a large application space in the precooling and fresh-keeping of fruit and vegetables.
查看更多>>摘要：This paper aims to experimentally investigate the heat transfer characteristics of pool boiling on horizontal U-shaped tubes in a large-scale confined space. The saturation temperature ranges from 20 to 40 degrees C and the heat flux varies from 2.5 to 10.5 kWm(-2). Two types of tubes with an outside diameter of 19.05 mm are tested: a smooth tube and a fin-enhanced tube with 0.4 mm fin height, 1220 fpm (fins per meter) and a 0.12 mm fin gap. The tubes are made of titanium with a length of 1165 mm. In case of pool boiling, the heat transfer coefficient for the tested tubes increases with increasing saturation temperature and heat flux. The fin-enhanced tube facilitates the bubble nucleation with the heat transfer coefficient enhancement factor varying in the range of 1.25 similar to 2.28. Furthermore, the experimental heat transfer coefficients are compared with four correlations obtained in the open literature. R-J correlation and Copper correlation are found to be the optimum correlation for the smooth tube and the enhanced tube with the mean relative error of 10.93% and 11.48%, respectively. Findings from this study can supply a fundamental basis for validation and improvement propane heat transfer performances for the intermediate fluid vaporizer (IFV) engineering design.
Burkov, I. A.Pushkarev, A., VRyabikin, S. S.Shakurov, A., V...
11页
查看更多>>摘要：Cryoablation is the most commonly used type of cryosurgery. Today, this treatment is insufficiently automated and therefore less accurate than alternative technologies that significantly limits and gradually reduces the scope of its application. However, from low temperature engineering point of view cryosurgery has the untapped potential of the improving its accuracy. In this paper three major methodological problems of cryosurgical equipment and procedure improving are considered: the impact on target isotherm location (1) of the soft biotissue moisture content solidification latent heat variation, (2) of the cryoprobe constructions and operating at maximum cooling power including the fluid cryogen features and the accuracy of boundary condition replacing a cryoprobe and (3) target isotherm fixation approach by modifying the cryoprobe operating mode. The numerical results showed that the target isotherm location depends insignificantly on different moisture content of soft biotissue, then it is not a limiting factor for cryoexposure prediction. Also numerical results showed that the theoretically minimum temperature of cryoprobe surface significantly overestimates their movement, this leads to a significant difference between the experimental and simulation results. The typical shape and movement of cryonecrosis isotherm at refined maximum cryoprobe cooling power for two typical constructions of cryoprobes and two cryogens are presented. The novel algorithm of modifying the cryoprobe operation mode for controlled precision cryosurgery is proposed and validated. All this complements the previously obtained data and shows the prospects for performing precision cryosurgery. The total average uncertainty of target isotherm location during the studied preliminary predicting stage of temperature field movement (virtual cryoablation) is estimated no more than +/- 0.41 mm. This information is expected to be useful for improving the quality of cryosurgery planning algorithms (e.g. for tumor treatment).
Hoang, Duy K.Olatunji, Jamal R.Lovatt, Simon J.Carson, James K....
10页
查看更多>>摘要：A computational fluid dynamics (CFD) simulation was developed to simulate an industrial cheese chilling process. Forced air chilling experiments were performed on blocks of agar (cheese analogue) to simulate the airflow and product arrangement in a section of an industrial cheese chilling tunnel. The flow field was solved at steadystate and decoupled from the heat transfer processes. The six blocks of agar were placed in a polystyrene test chamber that was in turn placed in an environmental testing chamber. Temperatures were measured at the surfaces and the geometric centre of the tested blocks of agar. Good agreement was observed between predicted and experimental data. Having been validated, the model was used to generate simple correlation models for predicting the volume-averaged temperature of blocks of cheddar cheese and mozzarella cheese during industrial chilling
查看更多>>摘要：Heat capacity and temperature matching between the heat sources and energy system is of vital importance to improve energy efficiency, especially in occasions with multiple temperature-distributed heat sources. In this paper, an improved ammonia-water absorption refrigeration system with additional intermediate-pressure generator and absorber is proposed, aiming at recovering two kinds of heat sources with different grades. To match the heat capacity of two sources, solution distribution to the high- and intermediate-pressure generator can be adjusted. Moreover, heating areas of the two generators are extended from the reboilers to the stripping sections, in order to improve the heat utilization ratio. Simulation study shows that as the solution split ratio to the intermediate-pressure generator increases, the capacity for recovering low-grade heat sources is improved. The coefficient of performance of the proposed system is 5% higher than that of the modified vapor exchange system within a large range of the intermediate pressure. Under the baseline working condition with evaporation temperature of -15 degrees C and condensation temperature of 31 degrees C, a significant increment in exergy efficiency is achieved by the proposed system, which is 32.6% and 56.5% higher than that of the conventional single-effect and conventional vapor exchange system, respectively.
Shaker Al-Sayyab, Ali KhalidNavarro-Esbri, JoaquinMota-Babiloni, Adrian
12页
查看更多>>摘要：This work presents an energy, exergy, and environmental evaluation of a novel compound PV/T (photovoltaic thermal) waste heat driven ejector-heat pump system for simultaneous data center cooling and waste heat recovery for district heating networks. The system uses PV/T waste heat with an evaporative-condenser as a driving force for an ejector while exploiting the generated electric power to operate the heat pump compressor and pumps. The vapor compression system assessed several environmentally friendly strategies. The study compares eleven lower global warming potential (GWP) refrigerants from different ASHRAE safety groups (R450A, R513A, R515A, R515B, R516A, R152a, R444A, R1234ze(E), R1234yf, R290, and R1243zf) with the hydrofluorocarbon (HFC) R134a. The results prove that the system presents a remarkable overall performance enhancement for all investigated refrigerants in both modes. Regarding the energy analysis, the cooling coefficient of performance (COPC) enhancement ranges from 15% to 54% compared with a traditional R134a heat pump. The most pronounced COPC enhancement is caused by R515B (a 54% COPC enhancement and 49% heating COP enhancement), followed by R515A and R1234ze(E). Concerning the exergy analysis, R515B shows the lowest exergy destruction, with the highest exergy efficiency than all investigated refrigerants.
查看更多>>摘要：To weaken the noise pollution of wet cooling towers, a large-scale wet cooling tower with a 660 MW unit is used as an example, and the water-splashing noise is measured in a field test. The sound source characteristics are determined based on the field test results, and the sound source surface is specified as the initial parameters of the simulation. Then, the noise propagation model for the wet cooling tower is established based on the ray tracing method, with a maximum relative error of only 2.22%. Two noise reduction schemes, vertical and curved sound barriers, are proposed based on this model. Furthermore, the noise reduction effects of two different types of sound barriers are investigated. Under identical conditions, the simulation reveals that the vertical sound barrier performs better than the curved sound barrier in terms of noise reduction. In addition, The results also show that a vertical sound barrier with a length of 90 m, a height of 10 m, and a distance of 15 m from the tower is an optimal scenario, with an A-weighted sound pressure level (A-SPL) of just 42.08 dB(A). In summary, the noise problem associated with wet cooling towers may be effectively addressed in this instance.
查看更多>>摘要：The piston offset in the helium valved linear compressor (VLC) deteriorates the cooling capacity and operation life of the Joule-Thomson (JT) refrigerator, especially in aerospace applications. To clarify the influence mechanism of operating parameters on the offset characteristic of the VLC, a relative quantitative investigation is theoretically and experimentally proposed. Based on the reliable VLC developed in our lab in the hope of using for the space infrared detector, the main parameters involving the charging pressure, operating frequency, piston displacement and valve opening are systematically studied. The offset amplitude, establishment time and start-up characteristic of the offset under different conditions are presented. The equation that contains all the operating parameters capable of describing the offset values is expressed. The polynomial fitting from the experimental data verifies the deduced equation, and further explains the interaction between the offset and the operating parameters quantitatively. This study can be an effective guidance in reducing or even eliminating the offsets to improve the performance of the VLC.
查看更多>>摘要：Research in the literature about using aluminum and copper heat pipes (HP) with different working fluids in refrigerated containers is limited. Therefore, an experimental investigation of a new potential of using two types of heat pipes for refrigerated container applications is conducted. The developed copper and aluminum HPs are experimentally investigated under various operating conditions with three working fluids. The copper heat pipe is investigated with ethanol, methanol, and acetone as the working fluids. The thermal performance aluminum HP is only investigated with acetone as a working fluid given the compatibility between the working fluid and the wall material. The developed HPs are investigated under a wide range of operating conditions in terms of input powers (5, 15, 30, 45, and 60 W), tilt angles (30 degrees, 45 degrees, 60 degrees, and 90 degrees), and filling ratios (15 % and 30 %). The condenser section of the HP is immersed in the bath containing dry-ice. Results show that the best thermal performance in terms of thermal resistance of 2.2 K/W is obtained, with copper HP with acetone as a working fluid at a filling ratio of 30 %, input power of 60 W, and vertical orientation. In addition, aluminum HP shows a competitive thermal performance with a minimum thermal performance of 2.6 K/W.
NSTL
Elsevier