冷水机组的选型研讨

以曲靖卷烟厂冷水机组的选型为例,通过对蒸汽溴化锂冷水机组和离心式冷水机组的能效、经济性、环保排放等方面进行比较,提出离心式冷水机组以其能效高、经济性好更显系统优异,并且环保效果显著。     

冷水机组辅助泵的节能改造

本文讲述了冷水机组的工作原理及如何对其辅助泵进行节能改造，并介绍了一个应用实例。     

OMRON小型PLC在食品包装机械、冷水机组控制系统中的应用

文章详细描述了OMRON小型PLC的配置和技术特点,提出了适合食品包装机械、冷水机组控制需要的控制系统,介绍了控制软件的功能。对于食品包装机械、冷水机组计算机监控系统的硬件和软件协议也做了详细的讨论。可以作为食品包装机械、冷水机组产品工程师的参考。     

磁悬浮变频离心式冷水机组能效实测研究

<正>一、引言永发印务（东莞）有限公司（下称“东莞永发”）中央空调采用螺杆式冷水机组，2 0 0 4年投入使用，至今已使用超过1 6年。自投入使用以来，未进行大范围的更新升级，随着设备的老化，能耗考核指标C O P值不断降低，电能利用率与出厂时相比已下降4 3%。由于设备已到报废期，故障频发，近三年来，每年维修费用超过1 0万元，且每年呈不断上升态势，消耗生产成本的同时，影响生产节奏。鉴于此，东莞永发于2021年8月对中央空调系统进行了改造升级，引入先进节能的磁悬浮冷水机组以节省能源。     

板管蒸发冷却螺杆式冷水机组的纺织空调应用

探讨板管蒸发冷却螺杆式冷水机组在纺织空调中的应用。介绍该型机组的制冷原理以及优良的性能特点。分析了现代纺织空调供冷特点、要求和采用板管蒸发冷却螺杆式冷水机组的适应性。通过工程实例比较得出,采用板管蒸发冷却螺杆式冷水机组比传统螺杆式水冷机组提高系统综合能效比15.6%,系统节电13%,节约冷却水补水量50%。认为:板管蒸发冷却螺杆式冷水机组具有系统简单、节水节电、机组一体化、节约占地面积、便于维护管理等优势,适用于新厂空调设计和老厂空调改造。     

板冰/冷水机组的运行特征及应用

相对于常规制冷系统,冰蓄冷系统由于有着诸多突出优点而越来越被重视并被广泛应用。冰蓄冷技术有多种类型,其中,以板冰/冷水机组为代表的动态冰蓄冷技术综合性能比较突出,是近年来研究的重点,本文着重论述了板冰/冷水机组的工作原理介绍了板冰/冷水机组的实际应用形式及领域,对其发展前景做了展望。     

溴化锂吸收式冷水机组的节能运行分析

溴化锂吸收式冷水机组的能耗约占空调系统总能耗的４０ ％ 左右,研究溴化锂吸收式冷水机组的节能措施对空调节能具有重要意义。文章结合工程实际提出的冷水机组变水温运行、冷却水变水量运行、改变冷却塔运行方式、重视冷却塔循环水、水处理等措施,取得良好的节能效果,易于在现有系统中实现。     

氟机供冷的麦汁一段冷却工艺的技术改造

国内啤酒行业进行麦汁一段冷却技改采用氨机供冷的比较多,而采用氟冷水机组供冷的企业比较少,采用氟冷水机组供冷的麦汁一段冷却技改不但不需要换蒸发器,而且传热效果比氨蒸发器好.本文介绍了氟机供冷的麦汁一段冷却的工艺流程、并从制冷技术的角度对一段冷却技改能提高氟机的制冷量进行深入阐述.     

新风独立处理系统在卷烟厂的应用及节能效果分析

为解决空调系统采用传统一次回风处理技术在热湿处理过程中存在冷热抵消、再热能耗高等问题,以贵定卷烟厂联合工房为对象,采用DeST建筑热环境设计模拟软件对全年冷热负荷进行模拟分析,以夏季负荷为重点,将其划分为室内负荷、新风负荷和再热负荷,设计了一种采用双温冷水机组的新风独立处理系统.其中,高温冷水机组提供高温冷冻水(16～...     

某复合型地产项目空调系统方案的比较与选择

从设备的初投资、运行费用、技术性能等方面,对某复合型地产项目空调系统方案的进行了比较,采用水冷螺杆式冷水机组明显优于风冷热泵机组,为该工程对空调系统的选择提供了依据。     

超低温氨用螺杆制冷机组性能综合评价的基本原则

综合分析了评价超低温氨用螺杆制冷机组性能和运行效率的四个基本综合评价原则,包括压缩机的可靠性;机组的节能装置效果;以及在部分负荷下的能效、制冷剂、噪声以及经济性。最后结合实际工程进行比较,为超低温速冻工程中氨用螺杆压缩式制冷机组的应用提供技术选型依据。     

Application of heat in postcook meat chillers reduces Listeria

Electrical air-blowing heaters were used to heat and dry out holding chillers used for postcook commercial processed meats in an attempt to control the presence of Listeria. A baseline study of the prevalence of Listeria in holding chillers in seven facilities was undertaken. Listeria was detected in four of the seven chillers, and swab samples showed Listeria prevalence ranging from 7 (7.8%) of 90 to 6 (20%) of 30, depending on the facility. Two of the facilities with established Listeria contamination (A and E) were chosen for further studies. The heating trials consisted of three individual heating interventions at each of the two facilities, with 2 weeks of postintervention sampling after each treatment. The initial Listeria prevalence in chiller A was 19 (10.6%) of 180, and treatment at 37°C for 36 h reduced prevalence to 3 (1.7%) of 180. The initial Listeria prevalence in chiller E was 7 (7.8%) of 90, and treatment at 50°C for 2 h reduced prevalence to 0 of 90. Both reductions were statistically significant at P < 0.01. The incorporation of these two simple chiller heating protocols into these facilities' good manufacturing practices has effectively reduced prevalence of Listeria in chillers.     

Energy consumption, rate of cooling and weight loss in beef chilling in UK slaughter houses

The energy consumption, cooling rate and weight loss were measured in 14 beef chillers in commercial use. Beef sides were removed from the chillers between 24 and 48 h after loading but a deep leg temperature of 7°C or less on unloading was achieved in only 4 of the chillers. The weight loss was between 1·1 and 2% after 24 h and between 1·5 and 2·3% after 48 h and its value was 20 times the cost of the energy used.

Energy consumption was related to ambient temperature and evaporator fan energy. Mean annual UK specific energy consumption was 116 kJ/kg and the estimated total UK consumption is 113 TJ. A target consumption of 70 kJ/kg is possible with existing technology and if achieved by all UK plants would save 42 TJ per year and increase profits in the industry by 26%.     

Evaluation of non-contact infrared thermometry for measuring the temperature of pig carcasses in chillers

An OPTEX Thermo Hunter infrared (IR) non-contact hand-held thermometer was examined to determine its suitability for measuring porcine carcass surface temperatures during chilling. The manufacturer claims that the unit has the capability of measuring a range of temperature between -50°C and 500°C, with a resolution of 0·1°C. The device allows for an automatic determination and adjustment of unknown emissivities of objects to be measured. The stability of the device was tested in the laboratory at 4 and 18°C and for accuracy against a known surface temperature. Tests were conducted in a commercial chiller to determined whether the device could detect temperature differences between carcasses, sites on one carcass and chillers. The results obtained were also examined for repeatability. The thermometer required a minimum initial stabilisation period of 120 min after which the results compared favourably with known surface temperatures. The chiller tests indicated that temperature differences could be detected between the various carcasses, sites on one carcass and chillers, and that the readings were reproducible. The device is best suited for determining temperature trends when overall accuracy is not essential. The device could also be useful in evaluating chiller performance.     

Assessment of airflow patterns inside six industrial beef carcass chillers

Airflow patterns determine process efficiency in beef carcass chilling. An experimental study of air velocity in six industrial chillers (three batch and three continuous systems) afforded a diagnosis of their overall operation. However, the original experimental method did not provide an ideal chiller design: only configurations that were a priori more favourable for carcass chilling than others were identified. To complete the study, calculations were performed using computational fluid dynamics techniques. Applied to a continuous beef carcass chiller, this helped correct a dysfunction revealed in the experimental diagnosis, resulting in a marked lack of ventilation throughout about half the volume of the plant.     

Monochloramine versus sodium hypochlorite as antimicrobial agents for reducing populations of bacteria on broiler chicken carcasses

Studies were conducted to compare the effect of sodium hypochlorite (SH) versus monochloramine (MON) on bacterial populations associated with broiler chicken carcasses. In study 1, nominal populations (6.5 to 7.5 log CFU) of Escherichia coli, Listeria monocytogenes, Pseudomonas fluorescens, Salmonella serovars, Shewanella putrefaciens, and Staphylococcus aureus were exposed to sterilized chiller water (controls) or sterilized chiller water containing 50 ppm SH or MON. SH at 50 ppm eliminated all (6.5 to 7.5 log CFU) viable E. coli, L. monocytogenes, and Salmonella serovars; 1.2 log CFU of P. fluorescens; and 5.5 log CFU of S. putrefaciens. MON eliminated all (6.5 to 7.5 log CFU) viable E. coli, L. monocytogenes, S. putrefaciens, and Salmonella serovars and 4.2 log CFU of P. fluorescens. In study 2, chicken carcasses were inoculated with P. fluorescens or nalidixic acid-resistant Salmonella serovars or were temperature abused at 25 degrees C for 2 h to increase the populations of naturally occurring E. coli. The groups of Salmonella serovar-inoculated or temperature-abused E. coli carcasses were immersed separately in pilot-scale poultry chillers and exposed to tap water (controls) or tap water containing 20 ppm SH or 20 ppm MON for 1 h. The P. fluorescens-inoculated group was immersed in pilot-scale poultry chillers and exposed to tap water (controls) or tap water containing 50 ppm SH or 50 ppm MON for 1 h. Carcasses exposed to the SH treatment had nominal increases (0.22 log CFU) in E. coli counts compared with controls, whereas exposure to MON resulted in a 0.89-log reduction. Similarly, average nalidixic acid-resistant Salmonella serovar counts increased nominally by 34% (41 to 55 CFU/ml) compared with controls on carcasses exposed to SH, whereas exposure to MON resulted in an average nominal decrease of 80% (41 to 8 CFU/ml). P. fluorescens decreased by 0.64 log CFU on carcasses exposed to SH and decreased by 0.87 log CFU on carcasses exposed to MON. In study 3, SH or MON was applied to the chiller in a commercial poultry processing facility. E. coli counts (for carcass halves emerging from both saddle and front-half chillers) and Salmonella prevalence were evaluated. Data from carcasses exposed to SH during an 84-day historical (Hist) and a 9-day prepilot (Pre) period were evaluated. Other carcasses were exposed to MON and tested during a 27-day period (Test). E. coli counts for samples collected from the saddle chiller were 25.7, 25.2, and 8.6 CFU/ml for Hist, Pre, and Test, respectively. E. coli counts for samples collected from the front-half chiller were 6.7, 6.9, and 2.5 CFU/ml for Hist, Pre, and Test, respectively. Salmonella prevalence was reduced from 8.7% (Hist + Pre) to 4% (Test). These studies indicate that MON is superior to SH in reducing microbial populations in poultry chiller water.     

An inverse lumped capacitance method for determination of heat transfer coefficients for industrial air blast chillers

An inverse model using lump body was developed to calculate heat transfer coefficients as a dynamic function of time. The model used sequential function specification algorithm to calculate surface heat flux from transient temperature measurements inside a lump body system. Transient temperature measurements were collected during cooling inside an industrial chiller at two different positions with different air velocities using four replicates for each position. The calculated surface heat flux was found to be very accurate as the maximum value of the root mean squares error (RMSE) for temperature is 0.045 °C, lower than the expected error form thermocouple measurements. The calculated heat flux was then used to calculate heat transfer coefficients as a dynamic function of cooling time followed by calculation of time average heat transfer coefficient using numerical integration. The approach developed here could be a pragmatic powerful dynamic method to model spatial variation of heat transfer coefficients for industrial chillers and freezers.     

Effect of incubation temperature on aerobic plate counts of beef and sheep carcasses

Australian regulations for microbiological testing of carcasses specify a number of incubation temperatures and media for meat processed at both domestic and export establishments. Accordingly, the effect of incubation temperature and media on aerobic plate counts of samples from beef and sheep carcasses was investigated. For both species, aerobic plate counts on Petrifilm incubated at 35 degrees C were significantly lower than those counts on Petrifilm and pour plates incubated at 25 and 30 degrees C, reflecting the inability of many psychrotrophs to grow at 35 degrees C. When samples were taken from carcasses that had been stored in abattoir chillers for periods between 16 h and 5 days, difference between counts at 35 degrees C versus those incubated at 25 and 30 degrees C became greater as the period of refrigerated storage increased. For export beef carcasses, the effect of this difference is minimal, since the vast majority of counts incubated at 35 degrees C are done on carcasses that have been chilled for less than 24 h and will not have a large proportion of psychrotrophs.     

Validating the efficacy of peracetic acid mixture as an antimicrobial in poultry chillers

Peracetic acid mixture (PAHP), which is a combination of peracetic acid and hydrogen peroxide, has been approved as an antimicrobial for use in poultry chillers. To validate its effectiveness, 85 ppm of PAHP was compared with the 30-ppm chlorine treatment in a commercial setting. In this trial, 100 carcasses were sampled for Salmonella and Campylobacter spp. prior to chilling and 100 carcasses were sampled after chilling. In all, 400 carcasses were sampled using 85 ppm of PAHP in the chiller and 400 carcasses were sampled using the chlorine treatment. PAHP at 85 ppm reduced Salmonella-positive carcasses by 92% exiting the chiller, whereas treatment with 30 ppm of chlorine reduced Salmonella by 57%. Additionally, PAHP reduced Campylobacter species-positive carcasses exiting the chiller by 43% while chlorine resulted in a 13% reduction. These results suggest that peracetic acid in combination with hydrogen peroxide may be an effective antimicrobial in poultry chiller applications.     

Effects of rigor attainment temperature on meat blooming and colour on display

This paper describes the colour properties of seven hot-boned, unstimulated beef striploins during rigor attainment at 9, 14 and 24°C, during blooming at 4°C, and after storage at -1°C for 0, 2 and 8 weeks. Immediately after rigor attainment (0 weeks of storage) full blooming, as judged by L* and chroma, took at least 12 h. After 2 and 8 weeks storage, blooming was complete within about 4 h. The exponential equations describing blooming were different for 0 weeks compared with 2 and 8 weeks. This difference can be explained in terms of oxygen consumption by meat freshly in rigor. At 0 weeks, meat that entered rigor at 24°C had the best bloomed colour, whereas at 2 and 8 weeks the 9°C treatment had the best and the 24°C the worst. The data set, which spanned a range of ultimate pH values and three rigor attainment temperatures, was used to estimate the value of early colour measurements (first 24 h post-rigor) in predicting colour during display several weeks later. As judged by correlation coefficients, early measurements of hue were the only ones useful. L* and chroma were poor predictors. This result, together with the knowledge that blooming is slow in the first 24 h post-rigor, casts doubt on the value of subjective or objective colour assessments made in chillers. Temperature of rigor attainment between 9 and 24°C did not affect the time of browning onset, nor the rate of browning. It was confirmed that meat with lower pH had higher chroma before and after blooming.