微波加热处理对牦牛肉加热损失率、嫩度及微观结构的影响

本研究以牦牛背最长肌为原料,通过SDS-PAGE分析、加热损失率测定、质构分析及石蜡切片方法研究了100%、80%及60%功率微波热处理对牦牛肉蛋白质完全变性加热终点的热损失、嫩度及微观结构的影响。实验结果表明,对于相同的微波功率,随着加热时间的延长,牦牛肉的加热损失率和剪切力均增大(p<0.05);牦牛肉肌纤维出现了更大程度的间隙和断裂,肌束变得更加混乱。80%功率处理组加热损失率高于60%和100%功率处理组(p<0.05),60%功率处理组剪切力高于80%和100%功率处理组(p<0.05)。研究结果认为,对于相同的加热时间,低功率微波处理牦牛肉的得率、嫩度及显微结构较好;而使用中高功率加热时,尽可能选择短的加热时间,获得的牦牛肉品质较高。

Influence of heat loss through probe electrical leads on thermal conductivity measurement with TPS method

The transient plane source(TPS)method is developed recently to measure the thermal conductivity of materials.In the measurement,the heating power is influenced by the heat which is transferred via the probe electrical leads.This fact further influences the measurement accuracy of thermal conductivity.To solve this problem,the influence of heat loss through the electrical leads on the heating power is studied theoretically.The mathematical formula of heat loss is deduced,and the corresponding correction model is presented.A series of measurement experiments on different materials have been conducted by using the hot disk thermal constant analyzer.The results show that the influence of the heat loss on the measurement is sensitive to different test materials and probes with different sizes.When the thermal conductivity of the material is greater than 0.2 W/(m·K),the influence of the heat loss is less than 0.16%,which can be ignored.As to the lower thermal conductivity materials,it is necessary to compensate the heat loss through the electrical leads,and the accuracy of thermal conductivity measurement can be effectively improved.

The green hydrolysis technology of hemicellulose in corncob by the repeated use of hydrolysate

To achieve green hydrolysis technology of hemicellulose through repeated using hydrolysate, the hydrolysis of hemicellulose in corncob was studied. The influence of repeated use of corncob hydrolysate on concentrations of D-xylose and L-arabinose was investigated. The loss rates of D-xylose in the prepared D-xylose solutions both with and without corncob, and repeated using corncob hydrolysate under identical acidity condition were discussed. The result shows that D-XyIOSe concentration and L-arabinose concentration are all gradually increas- ing with the growing time of repeated use of corncob hydrolysate. After the fifth repetition, the concentrations of D-xylose and L-arabinose are 196.7 g. L-1 and 22.0 g.L-1, respectively. Substance inhibiting the degradation of D-xylose is generated during repeated use of corncob hydrolysate, and the production is further proved by the change of D-xylose concentration and the loss rate of D-xylose over heating time.

Pyrolysis characteristics of rubber compositions in medical waste

Thermogravimetric study of rubber compositions （operating glove and catheter） in medical waste was carried out using the thermogravimetric analyser （TGA）,at the heating rate of 20 ℃/min in a stream of N2.The results indicate that the decomposition process of operating glove appears an obvious mass loss stage at 250-485 ℃,while catheter has two obvious stages at 240-510 ℃ and 655-800 ℃,respectively; both samples present endothermic pyrolysis reaction; the decomposition of operating glove and the first mass loss stage of catheter are in agreement with natural rubber pyrolysis; the second mass loss stage of catheter corresponds to CaCO3 decomposition.Based on the experimental results,a novel two-step four-reaction model was established to simulate the whole continuous processes,which could more satisfactorily describe and predict the pyrolysis processes of rubber compositions,being more mechanistic and conveniently serving for the engineering.

The influence of viscous heating on the entransy in two-fluid heat exchangers

In the present work, water and olive oil are taken as working fluids to study the influence of viscous heating on the entransy dissipation caused by heat transfer in two-fluid heat exchangers. The results show that the influence of viscous heating on the entransy loss associated with heat transfer can not be neglected for the liquids having large dynamic viscosity. The viscous heating effect maintains the heat transfer ability of the working fluids, relatively reduces the entransy loss in heat exchangers; the viscous heating effect relatively augments the entropy generation due to heat transfer and the available energy destruction in heat exchangers. For the working fluid having large dynamic viscosity, the increasing rates of the entransy and entropy generation contributed by the viscous heating are even larger than those contributed by heat transfer, when the mass flow rate of working fluid reaches a certain value under the fixed heat transfer area condition. Thus, the entransy loss rate decreases and the growth rate of entropy generation increases as the mass flow rate of the working fluid increases. Under the same other conditions, the heat transfer entransy loss rate and entropy generation rate per unit heat transfer rate obtained when the fluid having a smaller heat capacity rate is cold fluid are less than those obtained when the fluid having a smaller heat capacity rate is hot fluid.