Expansion Tank Research Articles

English

The aim of the study was to evaluate the quality of refrigerated raw milk from dairy farms located in Southwestern state of Goiás during the rainy and dry seasons. Fresh milk samples were collected from bulk tank and stored for 0, 24, 48 and 72 h for the evaluation of psychrotrophic microorganisms counts, titratable acidity, chemical composition, somatic cell count (SCC) and total bacterial count (TBC). In the rainy season, the average temperature of the refrigerated raw milk samples was 17.4, 6.0, 6.1 and 5.3°C and in the dry period, the average temperature was 9.2, 2.4, 3.8 and 1.4°C for 0, 24, 48 and 72 h of storage, respectively. The physicochemical characteristics of refrigerated milk were consistent with the maximum limits established by Brazilian legislation after storage for 72 h in expansion tanks; however, in the dry period, refrigerated milk should not remain stored for more than 24 h due to the high TBC values. The results of the microbiological analyses revealed failures in the cleaning of equipment and utensils used for milking, demonstrating need for greater hygiene in the collection and maintenance of refrigerated milk at the production source. Key words: Storage time, mastitis, refrigerated milk, hygiene.&nbsp

Transient behaviors of heavy water reflector system during postulated initiating events (PIEs)

This study investigates the transient thermal-hydraulic behaviors of a heavy water reflector system during various postulated initiating events (PIEs). The following events are considered in the analysis: (1) loss of heavy water system (HWS) flow, (2) heavy water leakage, (3) loss of secondary cooling flow, and (4) dilution of heavy water. The sequence of each event is described, and thermal-hydraulic parameters such as the heavy water temperature, system pressure, flow rate, and heavy water level are monitored. To regulate the HWS, the heavy water temperature at the outlet of the heavy water vessel, the heavy water level in the expansion tank, and the flow rate in the HWS are used as the reactor regulating system (RRS) setbacks. In the event of loss of HWS flow, the standby pump kicks off to recover it, and none of the RRS setback signals are triggered. In the event of heavy water leakage, a low-level RRS setback signal trips the reactor, and the temperature rise in the HWS is not significant. The total amount of heavy water leakage with a break at the outlet of the heat exchanger is approximately 550 L. In the event of loss of secondary cooling flow, a high-temperature RRS setback signal trips the reactor. In the event of heavy water dilution, a low-level RRS setback signal trips the reactor. In the case of a pipe rupture at the highest point in the HWS inside the pool, the RRS setback signal is triggered at 83.9 s from the initiation. At the instant of the reactor trip, the reactor power increases to 150% of full power because of the degraded purity of the heavy water––95.7%. For the event of heavy water dilution, a reactor protection system (RPS) setback such as the reactor power difference between a neutron detector and a gamma detector should be used to trip the reactor.

QUALIDADE DO LEITE CRU REFRIGERADO GRANELIZADO COLETADO NO SUDOESTE GOIANO

Objetivou-se com o presente estudo avaliar a qualidade microbiológica e físico-química do leite em diferentes sistemas de produção, oriundos de produtores individuais e coletivos, da região de Rio Verde – GO. Foram coletadas amostras de leite cru refrigerado, armazenadas em tanques de expansão de propriedades rurais e tanques isotérmicos da região do sudoeste goiano. As amostras foram analisadas eletronicamente quanto a CCS (Contagem de Células Somáticas), composição centesimal e a CBT (Contagem Bacteriana Total). Foram realizadas 51 coletas de amostras de leite em tanques da propriedade rural, sendo 12 coletas de ordenha mecânica e 39 de ordenha manual; 13 em tanques de produtores coletivos e 38 de tanques individuais. Também foram coletadas 52 amostras de leite cru refrigerado (coleta 1), 15 amostras de leite granelizado que foram coletadas após o término da rota nas propriedades rurais (coleta 2) e 15 amostras de leite granelizado que foram coletadas após a chegada ao estabelecimento processador (coleta 3). Os resultados foram analisados, estatisticamente, pelo programa SISVAR por meio do teste de Tukey, ao nível de 5% de significância. Em relação à composição centesimal, apenas o teor de gordura do leite cru refrigerado transportado a granel diferiu, significativamente, entre as coletas. Essa variação pode ter ocorrido devido ao procedimento de coleta das amostras, por uma possível falta de padrão da realização das mesmas. Os demais resultados não apresentaram diferença estatística, ao nível de 5% de significância, de acordo com o teste utilizado. As condições de granelização inadequadas do leite na fonte de produção influenciaram a qualidade microbiológica do leite, pois muitas amostras analisadas apresentaram contagens de CBT acima do permitido, de acordo com a legislação vigente. O leite ordenhado mecanicamente e oriundo de produtores individuais apresentaram CCS acima do limite estabelecido pela legislação brasileira. Medidas higiênico-sanitárias tomadas com mais critério são necessárias para que as características físico-químicas do leite sejam mantidas.

Discussions on the Methods of Preventing Heat Transfer Fluids from Oxidation in Open Heating System Based on Liquid-Phase Organic Heat Transfer Fluids Heater

Introduces the technological process of the open heating system with a liquid-phase organic heat transfer fluids heater by analyzing the advantages and disadvantages of preventing heat transfer fluids from oxidation based on expansion pipe with cooling water casing. And it presents two methods to prevent heat transfer fluids from oxidation by arranging directly cooling coils or pulsating heat pipes in the expansion tank; it also provides the schematic diagram of those methods as well as comparatively analyzes their advantages and disadvantages.

Investigations on single-phase natural circulation loop dynamics. Part 3: Role of expansion tank

Expansion tank is an important component of all single-phase natural circulation loops. The tank serves the twin purposes of venting the air out during the loop filling and accommodation of the swells and shrinkages of the loop fluid during the transient. In the present study, experimental investigations have been carried out in a rectangular single-phase natural circulation loop to bring out the role of expansion tank in loop dynamics. The results on loop stability and transient behavior are discussed. The experimental investigations show that there is significant amount of heat exchange between the main loop fluid and the expansion tank fluid. First, the results of experimental studies are presented. The different flow regimes observed in these experimental investigations are discussed. Next, a model is presented for taking into account the heat exchange between the main loop fluid and the expansion tank fluid. Finally, the model is applied to simulate the dynamic behavior of different single-phase natural circulation loops. The investigations carried out in this study have helped in resolving the issue of hysteresis observed in these loops.

소듐 시험루프 내 고온 압력용기의 크리프-피로 건전성 평가

본 연구에서는 한국원자력연구원 내에 설치될 예정인 소듐시험 시설인 SELFA(Sodium Thermalhydraulic Experiment Loop for Finned-tube Sodium-to-Air heat exchanger) 내에서 정상상태 가동온도가 510°C의 고온 압력용기인 팽창탱크에 대해 고온 건전성 평가를 수행하였다. 팽창탱크에 대해 3 차원 유한요소 해석에 기초하여 고온설계 기술기준인 ASME Section III Subsection NH 와 프랑스의 RCC-MRx 코드를 따라 크리프-피로 손상평가를 수행하였다. 평가결과 팽창탱크는 크리프-피로 설계 과도 하중 하에서 구조적 건전성을 유지하는 것으로 나타났다. 316L 스테인리스강 재질의 동 압력용기에 대해 정량적 코드 비교 분석을 수행하였다.

Milk Quality of Dairy Cattle Bred in Ceará, Northeast of Brazil

The demand for high quality dairy products is growing, milk should be produced under both sanitary and technological standards, to ensure maintenance of its nutritional characteristics and meet the required hygienic aspects. Our objectives were to evaluate the quality of refrigerated fresh milk from cattle, produced in the city of Magdalena, State of Ceara, Northeast of Brazil, according to the parameters set forth in regulatory instruction number 51, and compare the quality of milk in different breeding systems. 101 refrigerated fresh milk samples were collected monthly, from October 2010 to March 2011, directly from the expansion TANKS of three dairy farms, with different production systems. The samples were collected in vials containing Bronopol (2-bromo-2- nitropropane-1,3-diol), packaged and transported in thermal boxes with ice, and sent for analysis to the laboratory clinica do leite-ESALQ – USP, for total bacterial count (TBC), somatic cell count (SCC), and milk composition in relation to fat, protein, lactose, total solids (TS), dry degreased extract (DDE) contents. The patterns of chemical composition of milk, TBC and SCC observed were within the limits established by regulatory instruction number 51 in all samples, demonstrating that producers adopted hygienic measures for obtaining and conserving the milk, thus ensuring ITS quality. TN: NI 51 = Regulatory Instruction number 51, which regulates the production and transport of milk in Brazil.

Mechanical Analysis of the Energy Cycling Control for Further Smart Grid

Power electronic devices always consume a lot of energy, and this energy is then converted into heat, so that the device temperature rises. It will not only affect the device performance in full cycling, but also may result in damage, if the problem of heat dissipation can not be solved. In this paper, we propose an energy cycle approach that can provide a full utilization of the reused energy from the expansion tank to distributed pump. The Power distribution analysis of the controlling cabinet is presented together with the component in power cabinet. With the capacity of power electronic devices and power levels increasing rapidly, the thermal performance of the cooling system can be improved and higher requirements can be obtained.

Raw milk quality of individual and collective expansion tanks of a dairy industry located in Rio Pomba, Minas Gerais, Brazil - a case study

This study aimed to evaluate the microbiological and physico-chemical quality, and verify the occurrence of microbial growth inhibitors in raw milk maintained in expansion tanks of a dairy industry located in Rio Pomba, Minas Gerais, Brazil.. It was collected 36 samples of raw milk from 12 expansion tanks in three replicates and determined the count of mesophilic aerobic, psychrotrophic and proteolytic psychrotrophic microorganisms. It was also determined the somatic cell count, the occurrence of pus and inhibitors of microbial growth in milk samples. Moreover, it was determined physico-chemical composition of milk. It was found that 80.0% of samples were in disagreement with standards established by Normative Instruction n.o51, once mesophilic microorganisms and somatic cells counts were above 7,5 x 10 5 , in addition to the presence of pus and microbial growth inhibitors substances. Also, the count of psychrotrophic and proteolytic psychrotrophic microorganisms were high, which compromises production of dairy products such as cheese, UHT milk, among others. However, we found no irregularities in levels of protein, fat, lactose, and total solids. Therefore, the implementation of good agricultural practices during handling, storage and transportation of raw milk to the dairy industry is necessary in order to minimize financial losses during production and to obtain better quality and safety of dairy products.

Real gas effects on charging and discharging processes of high pressure pneumatics

The high pressure pneumatic system has been applied to special industries. It may cause errors when we analyze high pressure pneumatics under ideal gas assumption. However, the real gas effect on the performances of high pressure pneumatics is seldom investigated. In this paper, the real gas effects on air enthalpy and internal energy are estimated firstly to study the real gas effect on the energy conversion. Under ideal gas assumption, enthalpy and internal energy are solely related to air temperature. The estimation result indicates that the pressure enthalpy and pressure internal energy of real pneumatic air obviously decrease the values of enthalpy and internal energy for high pressure pneumatics, and the values of pressure enthalpy and pressure internal energy are close. Based on the relationship among pressure, enthalpy and internal energy, the real gas effects on charging and discharging processes of high pressure pneumatics are estimated, which indicates that the real gas effect accelerates the temperature and pressure decreasing rates during discharging process, and decelerates their increasing rates during charging process. According to the above analysis, and for the inconvenience in building the simulation model for real gas and the difficulty of measuring the detail thermal capacities of pneumatics, a method to compensate the real gas effect under ideal gas assumption is proposed by modulating the thermal capacity of the pneumatic container in simulation. The experiments of switching expansion reduction (SER) for high pressure pneumatics are used to verify this compensating method. SER includes the discharging process of supply tanks and the charging process of expansion tank. The simulated and experimental results of SER are highly consistent. The proposed compensation method provides a convenient way to obtain more realistic simulation results for high pressure pneumatics.

콤팩트형 태양열/지열히트펌프 하이브리드 냉난방 및 급탕 시스템 개발 및 성능분석

In this study,the compact type solar thermal and ground coupled heat pump hybrid system for space heating/cooling and hot water supply has been developed. This hybrid system was installed in Zero Energy Solar House(ZeSH) in KIER for the demonstration. The thermal performance and operational characteristics of this hybrid system were analysed especially. The results are as follows. (1) This hybrid system was designed in order to address the existing disadvantages of solar thermal/ground coupled heat pump system. For this design, all parts except solar collector and ground coupled heat pump were integrated into a single product in a factory. The compact type unit includes two buffer tanks, an expansion tank, pumps, valves, a controller, etc. This system has an advantage of easy installation with simple plumbing work even in narrow space. (2) The thermal charging and discharging time of the buffer tanks and its characteristics by ground coupled heat pump, and heat pump COP according to geo-source temperature and buffer storage temperature have been studied. This system was found to meet well to the heat load without any other auxiliary heating equipment. (3) The operating hours of the ground coupled heat pump as a backup device of solar thermal can be reduced significantly by using solar heat. It was also found that the minimum heating water supply setting temperature and maximum cooling water supply setting temperature make an influence on the heat pump COP. The lower heating water and the higher cooling water temperature, the higher COP. In this respect, the hybrid system`s performance can be improved in ZeSH than conventional house.

A novel thermally driven pump and its test in a supercritical CO2loop system

SUMMARY In this paper, a novel thermally driven pump is introduced, and its test in a closed supercritical CO2 loop cycle system is studied. The thermally driven pump is a refrigerant-circulating pump composed of two expansion tanks, which has less electricity consumption and better reliability compared with conventional mechanical pumps. Experimental results showed that the system efficiency of the present thermally driven pump in the supercritical CO2 loop can be enhanced compared with that using the mechanical feed pump. In addition, it was found that the system efficiency with the thermally driven pump decreases with the outlet temperature of condenser. The thermal energy utilization efficiency of the loop system with the thermally driven pump can be increased when the condenser has higher efficiency. Copyright © 2012 John Wiley & Sons, Ltd.

Characterization of microbiological quality of milk collected in expansion tank

For evaluation of microbiological conditions of raw milk and studies of some factors that influence their quality 24 properties were examined dairy located in the western region of Parana. There were three collections for aerobic mesophilic microorganism analysis and coliform and thermotolerant. There was also one collect for verification of microorganisms health quality indicators (coliform and thermotolerant) of the water of these properties. For the analysis of mesophilic microorganisms 83.33% meet the requirement for default count of Normative Instruction No. 62. For total coliform, 46.87% of the samples have been checked have values above the recommended. For coliforms thermotolerants, there was 31.25% of contamination in samples. Regarding water samples, all were in agreement with the resolution of Conama (2005) but the presence of coliform thermotoleran is undesirable. It is concluded that further changes are required during the production of milk, with improvements in the quality and hygiene of milk. .

Factors impacting the quality of milk tank community microregion in Juiz de Fora (MG)

Milk refrigeration at the farm in communitary bulk tanks is the alternative choice taken by small milk producers that were grouped into associations to conform to milk quality legislation in Brazil. This model is wide used in Zona da Mata region in Minas Gerais state where familiar agriculture and dairy cattle is historically a tradition farming. That are nowadays without capital and with low investment potential. The deficiency of the producers managing capacity, defective cleaning processes, improper management of milking, deficiency of the mastitis control programs, contaminated waters sourcers, among others. Are compromising the communitary milk quality. The aim of this study was to identify the critical contamination points of the milk during the refrigerated storage in communitary bulk tanks in two milk producers association in Lima Duarte city. The results of the milk evaluation from the producers associations in this study showed that among the demands of legislation, the requisite that had a higher percentage of samples and producers out of the limits specified is the microbiological Total Plate Count. The water used in the farms for cleaning of utensils and milking during procedures, as well as the one used in communitary tanks for cleaning of the milk cooling tanks and drums showed high contamination by coliforms. The assessments of cleaning surfaces that are in contact with the milk during cooling and storage showed that among the evaluated points, the output of the expansion tank and hose connections between reception and the expansion tank showed the worst results in relation to surface contamination. The results of this study indicate the need for training the producers to appropriate management of milking and to an improvement in the cleaning process of equipment and utensils in the farm. Likewise, in the tanks need to adopt standard procedures for cleaning and special attention to points which have the highest surface contamination. The water used in the cleaning process on the farm and in the communitary tanks requires treatment for not contributing to the to the contamination of dairy equipment surfaces.

Solar heat utilization for adsorption cooling device

This article deals with possibility of solar system connection with adsorption cooling system. Waste heat from solar collectors in summer is possible to utilize in adsorption cooling systems, which desorption temperatures have to be lower than temperature of heat transport medium operation temperature. For verification of work of this system was constructed on the Department of power engineering on University of Zilina solar adsorption cooling device. Solar equipment is used in the summer periods only partially for hot water, whereas is the lowest heat demand for heating, while solar collectors heat profits are currently the highest at this time. Therefore rises the idea of using this excess heat for cooling, because in summer is highest consumption of energy for cooling. 2. EXPERIMENTAL DEVICE Designed and constructed device is using for desorption from solar vacuum heat collector with field pipes. This is because these collectors have better performance and collectors to achieve higher operating temperatures than flat plate collectors. The collector has an effective area 3 m 2 . As a heat transfer medium in the collector circuits is used Alycol Thermo. The system does not work without electricity, because the collector circuit is not gravitational and works with forced circulation by using an electric pump. In the future, could the power supply not from electricity network, but from solar photovoltaic system. The proposed system is fitted with a device that needs a standard solar system (expansion tank, circulation pumps, heat exchangers, etc.). Cooling equipment is fitted with a system of tubes, pipes and valves.

Study of polytropic exponent based on high pressure switching expansion reduction

Switching expansion reduction (SER) uses a switch valve to substitute the throttle valve to reduce pressure for high pressure pneumatics. The experiments indicate that the simulation model well predicts the actual characteristics. The heat transfers and polytropic exponents of the air in expansion tank and supply tanks of SER have been studied on the basis of the experiments and the simulation model. Through the mathematical reasoning in this paper, the polytropic exponent can be calculated by the air mass, heat, and work exchanges of the pneumatic container. For the air in a constant volume tank, when the heat-absorption is large enough to raise air temperature in discharging process, the polytropic exponent is less than 1; when the air is experiencing a discharging and heat-releasing process, the polytropic exponent exceeds the specific heat ratio (the value of 1.4).

Performance study of supercritical CO2-based solar Rankine cycle system with a novel-concept thermally driven pump

In this article, a supercritical CO2-based solar Rankine cycle system (SRCS) with a novel-concept thermally driven pump is studied. The thermally driven pump is a refrigerant-circulating pump composed of two expansion tanks and having merits of low power consumption and high reliability in comparison with conventional mechanical pump. The application of the present thermally driven pump in the supercritical CO2-based SRCS shows that an oscillatory flow is realized in the system and the system thermal efficiency is enhanced compared to the SRCS using the mechanical feed pump.

Design and Implementation of a Machine to Increase the Life of Oil Immersed Transformers by Automatic Restoration of Silica Gel

The oil and paper of power transformers gradually age and consequently their quality decreases, which has an important effect on the lifetime of the transformer. The aging rate of these two materials depends on the temperature and moisture of the environment. The presence of moisture in a transformer deteriorates transformer insulation by decreasing both its electrical and mechanical strength. Hence, silica gel is used to absorb the water from the existing air between the environment and the expansion tank. Since the absorption capacity of silica gel decreases over time, it must be restored during the lifetime of the transformer. This paper evaluates the different effects of moisture on transformer insulation and describes a designed system: the automatic silica gel restoration machine. Applying this machine will increase the life of transformer insulation and consequently the duration of its useful life. The article presents some promising patents on life of oil immersed transformers by automatic restoration of silica gel.

Comparison between experimental data and numerical modeling for the natural circulation phenomenon

The study of natural circulation phenomenon has been object of crescent interest in scientific community in recent years. The new generation of compact nuclear reactors uses natural circulation of the fluid as a residual heat removal cooling system in case of accident or shutdown. The objective of this paper is to present a comparison between experimental data and numerical simulation results for the natural circulation phenomenon in single and two-phase flow regime. Experimental data were obtained from a circuit built with glass tubes, through which thermal hydraulic phenomenon visualization was possible. The circuit is composed of an electric heater as the heat source, a heat exchanger as the heat sink and an expansion tank to accommodate fluid density changes. Instrumentation data acquisition is performed through thermocouples and pressure meters, and controlled by a computer interface developed using LABVIEW. Numerical modeling and simulations were done with the thermal hydraulic code RELAP5, which is widely used for this purpose. The cyclic reverse flow observed in the circuit was well represented by the numerical model. The comparison demonstrated that the numerical simulations are very close to the experimental data.

Cavitation Damage in Flowing Liquid Sodium Using Venturi Test Section

The present paper describes the damage behavior caused by cavitation in flowing liquid sodium using venturi test section. The venturi test section was made from 316 SS with an inner diameter of 6.5 mm and a length of 20 mm. The experiment was conducted with pressure of argon cover gas in the expansion tank ranging from 105-110 kPa. The liquid sodium temperature was kept at 200°C and the sodium flow rate was 27-28 L/min, which corresponded to developed cavitation condition with the cavitation coefficient of 0.59-0.51. This condition was kept for 600 hours during the experiment. The results showed that cavitation bubbles collapse created damage on the inner surface of the venturi test section in the form of pits due to eroded surfaces. Under SEM, most of the pits on the inner surface of the venturi test section were in the sizes of around 25 µm. Some pits with sizes larger than 25 µm were also observed with the largest diameter around 110 µm which indicated intense collapse of cavitation bubbles. Observation on the inner surface of the test section also indicated some micro cracks, which might be caused by the cyclic process of the formation and collapse of the bubbles during cavitation process.