Constant Temperature Storage Research Articles

Isothermal Storage Delays the Senescence of Post-Harvest Apple Fruit through the Regulation of Antioxidant Activity and Energy Metabolism.

The purpose of this work was to elucidate the influence of TF (5 ± 5 °C, and 5 ± 1 °C) and CT (5 ± 0.1 °C served as an isothermal state) storage environment on the antioxidant ability and energy metabolism in post-harvest apple fruit during storage. Specifically, compared with fruit in TFs groups, the quality attributes of apples in the CT group, including firmness, fresh weight, contents of SSC, and TA were maintained at a higher level. In addition, fruit stored in the CT environment revealed a suppressed respiration rate and EL, lower MDA, O2·-, and H2O2 accumulation but increased the activities of SOD, CAT, APX, and GR. At the end of storage, the SOD, CAT, APX, and GR activities of fruit in the CT group were 38.14%,48.04%, 115.29%, and 34.85% higher than that of the TF5 group, respectively. Fruit in the CT environment also revealed higher AsA, GSH, total phenols, and total flavonoid content. In addition, fruit stored in the CT environment maintained higher ATP content, EC, and more active H+-ATPase, Ca2+-ATPase, CCO, and SDH. At the end of storage, the SDH and CCO activities of fruit in the TF0.1 group were 1.74, and 2.59 times higher than that in the TF5 group, respectively. Taken together, we attributed the fact that a constant temperature storage environment can retard the fruit senescence to the enhancement of antioxidant capacities and maintaining of higher energy status in apple fruit.

Digital twins for secure thermal energy storage in building

The purpose of this work is to explore the role of the safe and optimal scheduling of thermal energy storage systems in intelligent buildings in promoting sustainable economic development under Digital Twins (DTs) technology. Phase Change Material (PCM) has high energy density, constant temperature storage, small footprint, and long service life. Here, PCM is first placed in the indoor building structure, and the DTs technology is introduced. In the development of intelligent buildings, the data generated by the energy storage system of intelligent buildings in the real space can be mapped to the virtual space in real time for simultaneous analysis. In addition, the PCM wall structure and thermal network DTs model are designed for the intelligent building. In addition, the PCW structure is used to build a thermal energy storage and dispatch model of the smart thermoelectric building based on DTs. Finally, the model is evaluated and analyzed experimentally. The analysis of system optimization power under different schemes indicates that the scheduling operation strategy of thermal energy storage of building walls can avoid overcharging or over-discharging batteries in the microgrid and reduce battery power consumption. Besides, the building wall energy storage capacity is always in the range of 0.2 ∼ 0.8 on the all-weather scale. Moreover, the model constructed here achieves significantly lower economic costs, environmental costs, and energy costs and a better energy-saving effect than the existing model. The model built here can serve as experimental reference for further digital energy storage in intelligent buildings and comprehensive energy utilization because of its superior safety performance and lower consumption.

Performance analysis on the concentrated photovoltaic /thermal air collector with phase change material and vacuum double-glazing for temperature regulation

Although photovoltaic/thermal (PV/T) air collector has simple structure and strong pressure bearing capacity, there are problems such as low thermal efficiency, unstable output temperature, due to low heat transfer performance of air and fluctuating solar irradiation. To address the above issues, a concentrating photovoltaic/thermal air collector with phase change material and vacuum double-glazing (VDG-PCM-CPV/T) is proposed in this paper. The performance of VDG-PCM-CPV/T in three continuous days is studied and compared with the module with PCM and single-glazing (SG-PCM-CPV/T) and the module with single-glazing (SG-CPV/T) by establishing the mathematic model of the daytime and night. It is proven that VDG-PCM-CPV/T has certain advantages in alleviating the downward trend of air temperature caused by the decrease of solar irradiation, due to the constant temperature storage and heat release characteristics of PCM. At night, as the vacuum double-glazing has excellent heat preservation effect, the initial temperature of PCM in VDG-PCM-CPV/T is 5.00 °C higher than that of SG-PCM-CPV/T, enable VDG-PCM-CPV/T to obtain higher thermal efficiency in the next day. While, the electrical power of VDG-PCM-CPV/T is slightly lower than that of SG-PCM-CPV/T and SG-CPV/T. The exergy efficiency of VDG- PCM-CPV/T, SG-PCM-CPV/T and SG-CPV/T at peak is 1.70%, 1.10% and 2.00%, respectively.

Predictive model for growth of Clostridium botulinum from spores at temperatures applicable to cooling of cooked ground pork

Cooling deviations and temperature abuse are two main reasons leading to the risk of Clostridium botulinum outgrowth in cooked pork. The aim of this research was to create a model that could be used to estimate C. botulinum growth from spores in cooked pork at temperatures similar to those used to chill cooked pork in processing facilities and food establishments. A cocktail of proteolytic C. botulinum types A and B consisting of five strains per type were used to inoculate pork to a final spore concentration of approximately 2 log CFU/g and cooked to 71 °C to heat shock the spores and kill vegetative microbes. The growth of C. botulinum was established at constant storage temperatures from 10 to 46 °C. C. botulinum growth was also studied under dynamic temperature conditions with cooling set to start at 54.4 °C and end at 4.4 °C or 7.2 °C in monophasic or biphasic cooling profiles, respectively. Growth parameters were estimated using the Baranyi model as a primary model and growth rates were fitted using the modified Ratkowsky secondary model with respect to temperature. The R2 values ranged from 0.7653 to 0.9995 indicating that the Baranyi primary model was well suited to the growth data. The modified Ratkowsky secondary model's R2 was 0.9653 and its root mean square error (RMSE) was 0.0687. All 11 prediction error values computed were within the limit of acceptable prediction zone (−1.0 to 0.5) suggesting a good fit of the model. The predictive model can provide information for the safety of cooked pork exposed to longer chilling times or for customized process schedule development as cooling of larger diameter products presents a processing challenge in the meat process operations.

Constant Storage Temperature Delays the Senescence of Post-Harvest Apple Fruit Through the Regulation of Antioxidant Ability and Energy Metabolism

Constant Storage Temperature Delays the Senescence of Post-Harvest Apple Fruit Through the Regulation of Antioxidant Ability and Energy Metabolism

Thermotherapy and Storage Temperature Manipulations Limit the Production of Reactive Oxygen Species in Stored Pedunculate Oak Acorns

For many species, seed storage protocols are still being improved to provide viable seeds of the highest quality. Seed storage is extremely problematic for short-lived seeds categorized as recalcitrant, including pedunculate oak (Quercus robur L.), for which the optimal seed storage protocol involves a temperature of –3 °C and 40% acorn moisture content recommendations. The sensitivity of pedunculated oak seeds to temperature manipulations under preparation for long-term storage has been poorly investigated, particularly in terms of the production of reactive oxygen species (ROS), which are assumed to be determinants of seed longevity. Thermotherapy, the pathogen elimination procedure, did not increase the level of three types of ROS: hydrogen peroxide (H2O2), superoxide anion radical and hydroxyl radical (•OH). The temporal heat stress of thermotherapy resulted in slightly reduced levels of H2O2, indicating activation of the antioxidant systems in acorn preparation for storage. The effect of constant storage temperatures (−3, −5, −7 °C) and their combinations (−3 → −5 °C or −3 → −5 →−7 °C) on ROS levels and seed viability was investigated in three provenances. The highest ROS levels were detected in acorns stored at −7 °C, whereas three-step cold acclimation was beneficial for reducing ROS levels. Interestingly, the levels of H2O2 were not affected by temperature in thermotherapized acorns. In contrast, decreasing storage temperature caused a linear increase in •OH levels in all provenances. The effect of heat stress and cold stress on ROS levels in relation to long-term seed storage of pedunculate oak is discussed here in relation to the seed viability evidenced via germination rates, seedling emergence and electrolyte leakage. Thermotherapy and cold acclimation of acorns can improve their viability after storage by decreasing ROS levels.

Extension of Storage Life of Papayas Grown in Puerto Rico by Gamma Radiation Treatments

Shelf-life extension (measured as ripening delay) and the retention of nutrients in irradiated P. R. 965 papayas have been investigated at constant storage temperature and relative humidity. The major findings were: 1. The ripening process in irradiated papayas was delayed up to 7 days by the use of gamma radiation treatments. The maximum delay in ripening was achieved by 25 to 50 Krads treatments, while the 100 Krad treatment showed a slight stimulation of ripening in storage. 2. Some destruction of vitamin C (ascorbic acid) seemed to have been effected by the gamma irradiation, although there were only slight differences between dose levels. 3. The level of total carotenoids was not affected by gamma radiation. During storage, there was a marked increase in these pigments as the papayas ripened. 4. Gamma irradiation inhibited fungal proliferation on papaya fruit even at dosages of 25 Krad. 5. There was no effect observed at the dosages studied on the skin of the fruit which developed its characteristic bright yellow color when ripe.

Constant storage temperature delays firmness decreasing and pectin solubilization of apple during post‐harvest storage

The aim of this study was to evaluate the effect of storage temperature fluctuation (temperature variation cycles about 6 hr) on the firmness and pectin solubilization of “Fuji” and “Golden Delicious” during storage. Results showed that apples in 5 ± 0°C group showed the lowest firmness decreasing level (15.86% for “Fuji”, 24.76% for “Golden Delicious”) coupled with the minimum ethylene production, and the slowest inter-converting of chelate-soluble pectin and sodium carbonate-soluble pectin to water-soluble pectin compared with that of 5 ± 5°C and 5 ± 1°C. Moreover, the enzymatic activities (PG, PME, β-Gal, α-L-Af) were at the lowest level in 5 ± 0°C temperature fluctuation groups both of “Fuji” and “Golden Delicious”. Ultrastructural observations also revealed that constant temperature could restrain the solubilization of pectin and the dissolution of middle lamella. Besides, the impact of 5± 1°C on “Golden Delicious” was more significant relative to “Fuji”. In practical applications, the temperature supervision on “Fuji” could be appropriately relaxed compared with “Golden Delicious” during short-term storage. Novelty impact statement Constant storage temperature retarded the firmness decreasing by delaying the solubilization of cell wall pectin and suppressed the activities of cell wall degrading enzymes of “Fuji” and “Golden Delicious” cultivars. Constant storage temperature Constant storage temperature retarded the dissolution of the middle lamella between the cell walls of “Fuji” and “Golden Delicious” cultivars. “Golden Delicious” cultivar was more sensitive to the variation of storage temperature compared with “Fuji” cultivar.

Comparison of Fluctuating Thermal Regimes and Commercially Achievable Constant-Temperature Regimes for Short-Term Storage of the Alfalfa Leafcutting Bee (Hymenoptera: Megachilidae).

Interrupting the spring incubation of Megachile rotundata (F.) with a period of low-temperature storage for synchronizing the bees' emergence with crop bloom is an essential part of M. rotundata management. Previously, we demonstrated that bees exposed to thermoperiods (TPs) during low-temperature storage have higher survival rates than bees exposed to constant temperatures. But changing the temperature in the large mass of bees commonly found in most commercial settings would place considerable stress on the chambers' refrigeration system. Reducing the difference between a TP's cryophase and thermophase would decrease the stress on the refrigeration system. Therefore, we investigated a range of TPs with cryophases (12 h) of 6, 12, or 15°C and thermophases (12 h) of 15 or 18°C and compared the survival rates of these bees against bees exposed to constant temperatures of 12, 15, or 18°C. For eye-pigmented pupae, the TP 6-18°C and the control fluctuating thermal regime (FTR; 6°C with a daily 1-h pulse at 20°C) had the highest survival rates for the 2 yr tested. For the constant-temperature storage protocols, constant 15 and 18°C were either equivalent or lower survival than the control FTR. For emergence-ready adults, the 6-18°C TP had the highest survival rates. The constant 15°C and the control FTR had equivalent survival rates. Under the current constraints imposed by a commercial chamber's refrigeration system, interrupting M. rotundata spring incubation by exposing the developing bees to constant temperatures of 15-18°C is currently the best option for commercial operations.

The effect of the inlet temperature of the heat transfer fluid in a rectangular latent heat energy storage

Solar energy is available during the day only. The excess heat energy collected during sunshine hours can be stored in the thermal energy storage and it can be reused during off sunshine hours. Latent heat energy storage systems by using phase change materials (PCMs) can be used effectively for storing thermal energy. It has high-energy storage density and the constant temperature storage process. In this paper, the performance of the latent heat storage system and phase change characteristics of PCM inside a rectangular latent heat energy storage unit will be presented. In this study, purified water is used heat transfer fluid (HTF) which is passed through the copper tubes inside the test unit and commercial-grade paraffin wax is used as PCM and indirect contact heat transfer method is used to heat exchange from the HTF to PCM. It was found that the PCM at the upper layer of the test section first melted during the melting process. Moreover, the effects of inlet temperature of HTF on the charging process was investigated. It can be concluded that increasing the inlet temperature of HTF effectively decreases the total charging time of the melting process. The amounts of heat storage for the inlet temperature of HTF 70 °C and 80 °C are 7400 kJ and 6555 kJ respectively during the melting process.

Constant temperature during postharvest storage delays fruit ripening and enhances the antioxidant capacity of mature green tomato

The aim of this study was to evaluate the effect of storage temperature fluctuation (TF) (15 ± 5°C, 15 ± 1°C, and 15 ± 0°C) on the ripening quality and antioxidant capacity of mature green tomato. Results indicated that tomato subjected to high TF (15 ± 5°C) had higher respiration rate and weightlessness rate, earlier ethylene release peak, and developed rapid color transfer greater than that to 15 ± 0°C. Besides, tomato exposed to high TF (15 ± 5°C) reveal low lycopene, total phenols, and ascorbic acid content, and inferior activity of superoxide dismutase and catalase later in the storage period. Indicated in this study is the fact that a consistent storage temperature (15 ± 0°C) helps to delay ripening and the senescence process of mature green tomato, and a good sensory quality and high antioxidant capacity after storage is maintained. Practical applications Storage temperature fluctuation in cold chain logistics of fresh fruits and vegetables is one of the main factors leading to quality loss. In this experiment, the effects of different temperature fluctuations on ripening quality and antioxidant properties of mature green tomato were evaluated. The results showed that the high TF would lead to the abnormal ripening of tomatoes and reduce the ripening quality and antioxidant capacity, while the constant storage temperature had the opposite effect. Operators should ensure as far as possible that the temperature of any link in the cold chain logistics of fresh food is stable, so as to extend the full-ripening time of green mature tomato after harvest, and improve their edible quality and antioxidant capacity.

Estimation of real-time remaining shelf life using mean kinetic temperature

An easy estimation method for remaining shelf life based on food temperature history is presented. The impact of varying temperature history to a given time on food quality can be expressed by the mean kinetic temperature (MKT) as a single temperature effect. MKT is calculated by applying the linear interpolation method to constant storage temperature and food quality data at the time of estimation. The remaining shelf life could be point-estimated, assuming the future temperature to be consistent at MKT. The extreme temperatures experienced by the food are used as the future temperature to predict the range of remaining shelf life. The differences in remaining shelf life estimations using mean kinetic, minimum, and maximum temperatures at a given time increased initially and decreased to zero as they approached the food shelf life. This decrease indicates that the accuracy of the remaining shelf life improves as it reaches the food shelf life when the accuracy is most important.The developed method is applied to packaged chicken and low-temperature-pasteurized milk and is validated. The developed methodology could be applied to other foods as long as their food quality index change could be described as kinetic models.

Sizing a PV-Wind based hybrid system using deterministic approach

A designed model based on TRNSYS software is used to size a hybrid electrical renewable energy system that can be used to supply electrical load demands. The goal is to maintain a constant storage temperature of bitumen by compensating the thermal losses of bitumen tank through an immersed electrical heater. The developed model simulates the annual performance of different configurations of PV-Wind based Hybrid System (PWHS). It also provides the optimum configuration, which in turn, ensures supplying the needed energy with the lowest investment cost. On the other hand, a comparison study of two size deterministic methods, the yearly average month (YAM) and the worst month (WM) methods, is presented. The analysis of the designed TRNSYS model pinpoints the hybrid system requirements and the integration cost, and so far, assesses the economic and environmental impacts. Finally, the yearly average month method has served to size a grid-tied hybrid system with a lower integration cost compared to the worst month method. It’s important to note that the latter method also has served to size adequately in the isolated area.

The effect of different precooling rates and cold storage on milk microbiological quality and composition

The objective of this study was to measure the effect of different milk cooling rates, before entering the bulk tank, on the microbiological load and composition of the milk, as well as on energy usage. Three milk precooling treatments were applied before milk entered 3 identical bulk milk tanks: no plate cooler (NP), single-stage plate cooler (SP), and double-stage plate cooler (DP). These precooling treatments cooled the milk to 32.0 ± 1.4°C, 17.0 ± 2.8°C, and 6.0 ± 1.1°C, respectively. Milk was added to the bulk tank twice daily for 72 h, and the tank refrigeration temperature was set at 3°C. The blend temperature within each bulk tank was reduced after each milking event as the volume of milk at 3°C increased simultaneously. The bacterial counts of the milk volumes precooled at different rates did not differ significantly at 0 h of storage or at 24-h intervals thereafter. After 72 h of storage, the total bacterial count of the NP milk was 3.90 ± 0.09 log10 cfu/mL, whereas that of the precooled milk volumes were 3.77 ± 0.09 (SP) and 3.71 ± 0.09 (DP) log10 cfu/mL. The constant storage temperature (3°C) over 72 h helped to reduce bacterial growth rates in milk; consequently, milk composition was not affected and minimal, if any, proteolysis occurred. The DP treatment had the highest energy consumption (17.6 ± 0.5 Wh/L), followed by the NP (16.8 ± 2.7 Wh/L) and SP (10.6 ± 1.3 Wh/L) treatments. This study suggests that bacterial count and composition of milk are minimally affected when milk is stored at 3°C for 72 h, regardless of whether the milk is precooled; however, milk entering the tank should have good initial microbiological quality. Considering the numerical differences between bacterial counts, however, the use of the SP or DP precooling systems is recommended to maintain low levels of bacterial counts and reduce energy consumption.

Effects of storage period on kinematic viscosity and density of biodiesel and its blends with ultra-low-sulfur diesel fuel at constant storage temperature

Effects of storage period on kinematic viscosity and density of biodiesel and its blends with ultra-low-sulfur diesel fuel at constant storage temperature

Heat Transfer Enhancement for site level indirect heat recovery systems using nanofluids as the intermediate fluid

In this paper, implementation of nanofluids as a Heat Transfer Enhancement technique in Process Integration has been studied. A step by step flowchart is introduced and as a case study the effect of replacing water with various nanofluids as the heat transfer media in an industrial Heat Recovery Loop (HRL) has been modelled. Nanofluids are prepared by distributing a nanoparticle through a base fluid such as water, ethylene glycol or oils. Suspended nanoparticles slightly affect the thermal and physical properties of the base fluid. Primarily nanoparticles are added to improve the fluid’s heat transfer characteristics by increasing its Reynolds number and thermal conductivity. HRL system in a large dairy factory in New Zealand has been studied as case study. Results show that by applying various HRL design methods and a nanofluid as an intermediate fluid, an increase in heat recovery is possible without the need for extra heat exchanger area and infrastructure. 1.5vol.% CuO/water nanofluid has been chosen as an intermediate fluid and by using a constant temperature storage control strategy, heat recovery from liquid–liquid heat exchangers increases between 5% and 9%. The air-side heat transfer coefficient limits the impact of using a nanofluid for the air–liquid exchangers. In other cases, the total available duty from the process stream, such as a condenser, significantly nullifies the heat transfer benefit of using a nanofluid in a retrofit situation. Alternative to increasing heat recovery, results show that applying a nanofluid in the HRL design phase enables heat exchanger area to decrease significantly for liquid–liquid matches. Results show that the increase in pressure drop and friction factor effects in such a system is negligible.

Effects of Controlled Atmosphere Storage and Temperature on Quality Attributes of Mango

This study was conducted to analyze the effects of Controlled Atmosphere Storage (CAS) and low temperatures on quality attributes of cv. Keitt mango. Mango is one of the choicest fruits in the world and popular due to its delicious taste, pleasant aroma and nutritional value. To date, only 3% of the total world production is being exported due to the perishable nature of the product, lack of proper storage and other postharvest related diseases. Post-harvest loss of mango in Ethiopia is estimated to be between 25-40% and would occur during handling, transportation and storage. Storage loss could arise owing to atmospheric conditions and temperature. CAS is agricultural technologies which monitor and adjust constantly the level of CO2 and O2 within storage to reduce the rate of physiological and biochemical changes, ethylene sensitivity and incidence of decay development of mangoes and also inhibit pathogen growth. Thus, this study was under taken to determine the optimum storage conditions of Ethiopian mango in order to reduce considerable postharvest mango losses. In this work, randomized block design experimental was employed for optimization of the influencing factors mainly CAS and temperatures. Accordingly, experiments were carried out at constant storage temperature of 7°C with different atmospheric conditions of A (10% CO2+6% O2+84% N2), B (8% CO2+6% O2+86% N2), C (5% CO2+5% O2+90% N2) and Control (0.03% CO2+21% O2+79% N2). Besides, fruits also stored at different constant temperatures of 7°C, 10°C, 13°C and control (21-24°C) respectively. The result obtained showed that effect of CAS on quality attributes (weight loss and firmness) of cv. Keitt mango significantly improved the storage life as compared to that stored at ambient atmosphere with list significant difference values being at 0.05=3.12 and 1.708 respectively. In addition, the effect of temperature on Total soluble solid, Titrable acidity, pH, weight loss, firmness and skin color was found to be significant in prolonging the storage life of the fruit with List significant difference values of 0.05 (0.317, 6.58, 3.46, 4.148, 6.50 and 2.41). The study revealed that the fruit stored at 7°C under 10% CO2+6% O2 storage condition, as confirmed by sensory analysis, was given better preference to extend cv. Keitt mango up to 6 weeks. On the other hand, the fruits stored at 13°C with no CAS conditions showed better storage time of up to 21 days without chilling injury effect. Finally, it can be conclude that application of CAS technology can significantly enhance the quality and storage life thereby minimizing post-harvest losses of mango fruit.

Prediction of growth of Pseudomonas fluorescens in milk during storage under fluctuating temperature

Accurate prediction of growth of undesirable organisms (e.g., Pseudomonas fluorescens) in perishable foods (e.g., milk), held under sub-ideal storage conditions, can help ensure the quality and safety of these foods at the point of consumption. In this investigation, we inoculated sterile milk with P. fluorescens (~103cfu/mL) and monitored inoculum growth behavior at constant and fluctuating storage temperatures. Three storage temperatures, 4°C, 15°C and 29°C, were selected to simulate proper refrigeration conditions (4°C) and temperature abuse, respectively. To simulate temperature fluctuation, milk held at 4°C was subjected to temperature shifts to 15°C or 29°C for 4 to 6h. A modified logistic model was used to obtain the best-fit curve for the microbial growth under constant storage temperature. The specific growth rates at 4°C, 15°C, and 29°C, obtained from experimental data, were 0.056±0.00, 0.17±0.05, and 0.46±0.02h−1, respectively, and the lag time values were 29.5±4.2, 12.7±4.4, and 2.8±0.3h, respectively. A model predicting bacterial growth under different temperature fluctuations was obtained using the growth parameters extracted from constant temperature experiments. Growth behavior predicted by the fluctuating temperature model and that obtained experimentally were in good agreement. Lag time exhibited a larger variation compared with specific growth rate, suggesting that it depends not only on growth temperature but also on the sample population and temperature gradient. Additionally, experimental data showed that changing the temperature during the lag phase induced an additional lag time before growth; however, no significant lag time was observed under the temperature fluctuation during the exponential phase. The results of this study provide information for precise shelf-life determination and reduction of food waste, particularly for milk and milk-containing food products.

Modelling and predicting growth of psychrotolerant pseudomonads in milk and cottage cheese

Mathematical models were developed and evaluated for growth of psychrotolerant pseudomonads in chilled milk and in cottage cheese with cultured cream dressing. The mathematical models include the effect of temperature, pH, NaCl, lactic acid and sorbic acid. A simplified cardinal parameter growth rate model was developed based on growth in broth. Subsequently, the reference growth rate parameter μref25°C-broth of 1.031/h was calibrated by fitting the model to a total of 35 growth rates from cottage cheese with cultured cream dressing. This resulted in a μref25°C-cottage cheese value of 0.621/h. Predictions from both growth rate models were evaluated by comparison with literature and experimental data. Growth of psychrotolerant pseudomonads in heat-treated milk (n=33) resulted in a bias factor (Bf) of 1.08 and an accuracy factor (Af) of 1.32 (μref25°C-broth), whereas growth in cottage cheese with cultured cream dressing and in non-heated milk (n=26) resulted in Bf of 1.08 and Af of 1.43 (μref25°C-cottage cheese). Lag phase models were developed by using relative lag times and data from both the present study and from literature. The acceptable simulation zone method showed the developed models to successfully predict growth of psychrotolerant pseudomonads in milk and cottage cheese at both constant and dynamic temperature storage conditions. The developed models can be used to predict growth of psychrotolerant pseudomonads and shelf life of chilled cottage cheese and milk at constant and dynamic storage temperatures. The applied methodology and the developed models seem likely to be applicable for shelf life assessment of other types of products where psychrotolerant pseudomonads are important for spoilage.

Heat Transfer Enhancement in Heat Recovery Loops Using Nanofluids as the Intermediate Fluid

In this paper, the effect of replacing water with various nanofluids as the heat transfer media in an industrial Heat Recovery Loop (HRL) have been modelled. Generally, nanofluids are prepared by distributing a nanoparticle through a base fluid such as water. Suspended nanoparticles slightly affect the thermal and physical properties of the base fluid. Primarily nanoparticles are added to improve the fluid’s heat transfer characteristics by increasing its Reynolds number and thermal conductivity. Results show that by applying various HRL design methods and a nanofluid as an intermediate fluid, an increase in heat recovery is possible without the need for extra heat exchanger area and infrastructure. With the addition of 1.5 vol.% CuO nanoparticles to the HRL fluid using constant temperature storage method, heat recovery from liquid-liquid heat exchangers increases between 5 % and 9 %. In the case of air-liquid exchangers, the air-side heat transfer coefficient limits the impact of using a nanofluid. In other cases, the duty available from the process stream, such as a condenser, significantly restricts the heat transfer benefit of using a nanofluid. Alternative to increasing heat recovery, results show that applying a nanofluid in the HRL design phase enables heat exchanger area to decrease significantly for liquid-liquid matches.