scholarly journals Effects of an Air Curtain on the Temperature Distribution in Refrigerated Vehicles Under a Hot Climate Condition

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Lin Cong ◽  
Qinghua Yu ◽  
Geng Qiao ◽  
Yongliang Li ◽  
Yulong Ding
Keyword(s):  
Energy Dissipation ◽  
Air Temperature ◽  
Cold Chain ◽  
Airflow Rate ◽  
Open Door ◽  
Air Curtain ◽  
Hot Air ◽  
Hot Climate ◽  
Perishable Goods ◽  
Cold Energy

Refrigerated vehicle plays an essential role in the cold-chain applications. It directly affects the quality and shelf life of specialized perishable goods. However, the cold energy dissipation caused by natural convection through an open door during partial unloading breaks the isothermal cold environment and notably elevates the air temperature inside the refrigerated container. This temperature rise is harmful to the remaining food. In this study, an air curtain was introduced near the container doorway to attempt to reduce the cold energy dissipation caused by partial unloading. A numerical model was established to explore the effects of the key parameters of the air curtain such as the airflow rate, nozzle width, and jet angle on the air flow and temperature evolution inside the refrigerated container after the door is opened. The numerical results show that the key parameters need to be tailored to form a stable and effective air curtain for preventing the internal cold energy loss or external hot air invasion. An effective and stable air curtain was formed to make the inner air temperature increase only by about 3 °C from the initial temperature of 5 °C after the door was opened, when the jet velocity was set to 2 m/s, the nozzle width was set as 7.5 cm, and the jet angle was set between 0 deg and 15 deg. This work can offer significant guidance for the introduction of an effective air curtain in a refrigerated vehicle to avoid the failure of cold-chain transportation.

Phase Change Material to Reduce Cooling Load of Buildings in Hot Climate

2019 ◽  
Vol 801 ◽  
pp. 416-423
Author(s):  
Mahmoud Haggag ◽  
Ahmed Hassan ◽  
Shaimaa Abdelbaqi
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Air Temperature ◽  
Air Conditioning ◽  
Cooling Effect ◽  
Airflow Rate ◽  
Duct System ◽  
Air Velocity ◽  
Hot Climate ◽  
Change Material

Due to the hot climate of the United Arab Emirates (UAE), where the external ambient temperature may reach 50°C in the summer season, almost 75% of the total energy is consumed in air-conditioning (AC). A significant improvement in the AC systems performance during hot summer time aligned with energy conservation could be achieved by pre-cooling of the air entering the condensers. Inclusion of Phase Change Material (PCM) as thermal energy storage (TES) have been widely used as one of the environmentally friendly energy saving materials due to its high energy density. The absorption/releasing of heat by PCM during its phase change, provides a latent heating/cooling for the surrounding. Numerous systems have implemented PCM based-TES for cooling purposes, such as thermally activated building systems (TABS), suspended ceilings, external facades or in the ventilation system. This study examines PCM based air pre-cooling concept and evaluates its performance in extremely hot climate of UAE. The drop in the outlet air temperature of the duct system quantifies the cooling effect. A paraffin based PCM with melting range of 30–33°C integrated in containers placed in the test chamber mimic the air conditioning duct system, and its cooling effect is monitored. A Conjugate heat transfer model employing enthalpy-based formulation is developed to predict the optimized PCM container size and optimum airflow rate validated with experimental data. Single and series columns of PCM containers subjected to different levels of supplied air velocity at range of 1 m/s - 4m/s are evaluated. Employing series of PCM enclosures at low air velocity of 1m/s enhanced the pre-cooling performance and reduced the outlet air temperature to 35°C yielding a temperature drop up to 11°C.

scholarly journals Effect of Roof Cooling and Air Curtain Gates on Thermal and Wind Conditions in Stadiums for Hot Climates

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3941
Author(s):  
Fangliang Zhong ◽  
Hassam Nasarullah Chaudhry ◽  
John Kaiser Calautit
Keyword(s):  
Energy Consumption ◽  
Electric Energy ◽  
Building Energy ◽  
Future Research ◽  
World Cup ◽  
Air Curtain ◽  
Hot Air ◽  
Computational Fluid Dynamics Cfd ◽  
Energy Consumptions ◽  
The Spectator

To host the 2022 FIFA World Cup, Qatar is facing the greatest challenge in balancing the energy consumptions for cooling the stadiums and the thermal comfort for both players and spectators. Previous studies have not considered using a combined configuration of air curtain and roof cooling supply slot in stadiums to prevent the infiltration of outside hot air and reduce the cooling system’s energy consumption. This paper presents a Computational Fluid Dynamics (CFD) study of thermal and wind modeling around a baseline stadium and simulates the cooling scenarios of air curtains and roof cooling along with the energy consumption estimations for the World Cup matches using Building Energy Simulation (BES). Sensitivity analysis of different supply speeds and supply temperatures of air curtain gates and roof cooling was carried out, and the results showed that scenario six, which provides supply air of 25 m/s and 20 m/s at the roof and air curtain gates with a supply temperature of 10 °C, demonstrates optimal thermal performances on both the spectator tiers and the pitch. Compared with the baseline stadium performance, the average reductions in temperature on the pitch and spectator tiers under scenario six could reach 15 °C and 14.6 °C. The reductions in the Predicted Percentage of Dissatisfied values for the upper and lower tiers as well as the pitch were 63%, 74%, and 78%. In terms of the estimated energy consumptions, scenario six would consume electric energy per match at a rate of 25.5 MWh compared with 22.8 MWh for one of the stadiums in the 2010 South Africa World Cup and 42.0 MWh for the 2006 Germany World Cup. Future research is recommended to explore the influence of supply angle on air curtain gates and roof cooling supply slots’ performances.

Improving the Boiler Efficiency by Optimizing the Combustion Air

2015 ◽  
Vol 787 ◽  
pp. 238-242 ◽  
Author(s):  
R. Pachaiyappan ◽  
J. Dasa Prakash
Keyword(s):  
Heat Transfer ◽  
Water Temperature ◽  
Steam Generator ◽  
Air Temperature ◽  
Flue Gas ◽  
Maximum Heat ◽  
Air Preheater ◽  
Hot Air ◽  
Boiler Efficiency ◽  
Efficient Combustion

Air pre-heater and economizer are heat transfer surfaces in which air temperature and water temperature are raised by transferring heat from other media such as flue gas. Hot air is necessary for rapid combustion in the furnace and also for drying coal in milling plants. So an essential boiler accessory which serves this purpose is air pre-heater. The air pre-heater is not essential for operation of steam generator, but they are used where a study of cost indicates that money can be saved or efficient combustion can be obtained by their use. The decision for its adoption can be made when the financial advantages is weighed against the capital cost of heater. The efficiency of the boiler increases with the increase in the temperature of the combustion air used in the furnace. This is achieved by the increased temperature of the flue gas in the air preheater and economizer zone. This paper deals with the different ways to obtain the maximum heat from the flue gas travelling through the air preheater and the economizer zone to improve the boiler efficiency.

Temperature Distribution of Hot Air Flow in Heating Zone for Drying Application

2014 ◽  
Vol 627 ◽  
pp. 153-157
Author(s):  
Nawadee Srisiriwat ◽  
Chananchai Wutthithanyawat
Keyword(s):  
Temperature Distribution ◽  
Air Temperature ◽  
Power Supply ◽  
Air Flow ◽  
Heating Zone ◽  
Velocity Control ◽  
Rectangular Duct ◽  
Air Velocity ◽  
Hot Air ◽  
Set Up

The temperature distribution of hot air flow in heating zone of a rectangular duct has been investigated for drying application. The experimental set-up consists of a heater and a fan to generate the hot air flow in the range of temperature from 40 to 100°C and the range of air velocity between 1.20 and 1.57 m/s. An increase of the heater power supply increases the hot air temperature in the heating zone while an increase of air velocity forced by fan decreases the initial temperature at the same power supply provided to generate the hot air flow. The temperature distribution shows that the hot air temperature after transferring through air duct decreases with an increase of the length of the rectangular duct. These results are very important for the air flow temperature and velocity control strategy to apply for heating zone design in the drying process.

scholarly journals Drying kinetics and quality aspects during heat pump drying of onion (Allium cepa L.)

2012 ◽  
Vol 1 (2) ◽  
Author(s):  
Nihar Ranjan Sahoo ◽  
Uma Sankar Pal ◽  
Sanjaya Kumar Dash ◽  
M.D. K. Khan
Keyword(s):  
Heat Pump ◽  
Air Temperature ◽  
Colour Change ◽  
Coefficient Of Determination ◽  
Drying Time ◽  
Hot Air ◽  
Thin Layer Drying ◽  
Quality Aspects ◽  
Heat Pump Drying ◽  
Air Dryer

A prototype heat pump dryer has been developed for drying of fruits and vegetables at low temperature and relative humidity to maintain the quality of dried product. Onions, of Nasik red variety were peeled, trimmed and sliced to 2 mm thickness. The onion slices were dried in the heat pump dryer at 35ºC (32 % R.H.), 40ºC (26 % R.H.), 45ºC (19 % R.H.) and 50ºC (15 % R.H.). Samples were also dried in a hot air dryer at 50ºC (52 % R.H.) for comparison. The drying rate increased with increase in drying air temperature, associated with reduced R.H., in the heat pump dryer. Drying took place mainly under the falling rate period. The Page equation, resulting in a higher coefficient of determination and lower root mean square error, better described the thin-layer drying of onion slices than the Henderson and Pabis equation. Heat pump drying took less drying time of 360 min and yielded better quality dried product, with higher retention of ascorbic acid and pyruvic acid and lower colour change, as compared to a hot air dryer at the same drying air temperature of 50ºC.

scholarly journals INFLUENCES OF MALTODEXTRIN AND HOT AIR TEMPERATURE ON LOSSES OF BETACYANIN AND ANTIOXIDANT CAPACITY IN BEETROOT JUICE SPRAY DRYING

2018 ◽  
Vol 55 (5A) ◽  
pp. 92
Author(s):  
Lai Quoc Dat
Keyword(s):  
Antioxidant Capacity ◽  
Thermal Effect ◽  
Spray Drying ◽  
Air Temperature ◽  
Total Solid ◽  
Solid Content ◽  
Antioxidant Compounds ◽  
Beetroot Juice ◽  
Total Solid Content ◽  
Hot Air

Beetroot (Beta vulgaris L.), which is rich in betacyanin and antioxidant compounds, has been utilized as a good source of red pigment and antioxidants. Nevertheless, these compounds are thermally sensitive, consequently, being degraded in processes conducted at high temperature. This research focused on effects of maltodextrin and hot air temperature on losses of betacyanin and antioxidant capacity in spray drying of beetroot juice. Results indicated that adding maltodextrin and temperature of hot air significantly influenced on loss by thermal effect, consequently, on the recovery yield of betacyanin and antioxidant capacity of beetroot juice powder. Adding maltodextrin enhanced protection of betacyanin and antioxidants in beetroot juice against thermal effect. Increasing temperature of hot air caused increase in loss by thermal effect of betacyanin and antioxidant capacity. The loss of antioxidant capacity by thermal effect was higher than that of betacyanin. Results also indicated that the suitable conditions of spray drying of beetroot juice are adding maltodextrin to reach 30 % w/w of total solid content and 150 oC of hot air temperature.   

Cold Chain Logistics in India

2016 ◽  
pp. 159-172 ◽  
Author(s):  
Swapnil Saurav ◽  
Ravi Potti
Keyword(s):  
Supply Chain ◽  
Fruits And Vegetables ◽  
Critical Role ◽  
High Energy ◽  
Cold Chain ◽  
Temperature Sensitive ◽  
Horticultural Crops ◽  
Perishable Goods ◽  
Power Deficit ◽  
Marine Products

Cold Chain refers to the transportation of temperature sensitive products like perishable goods from the point of origin to point of consumption in the food supply chain, which keeps it fresh and edible for a much longer period than in normal conditions. Cold Chain helps in transporting seasonal products and also making it available throughout the year. Two main parts of cold chain are transportation and storage systems. The key Indian industries where cold chain logistics play very important role are fruits and vegetables, milk and milk products (ice cream), Poultry and processed meat, marine products, pharmaceutical (mainly vaccines) and chemicals. An efficient cold chain industry ensures availability of food products as well as prevents spoilage of medicines. Country like India, where infrastructure is one of the major challenges, cold chain plays a critical role. Analysis for this study shows that cold supply chain network does not differ significantly from products to products at least in Indian scenario. Some of the challenges to the growth of sector in India are high energy cost, power deficit, rising real estate cost, lack of logistical support and uneven distribution of capacity. All these challenges bring down the operating margin of a company and makes it not so attractive business sector. But during last couple of years there is a positive environment being created for this sector in India. The growth in organized retail, growing interest in horticultural crops, demand for cold chain logistics from Pharmaceutical industry and various initiatives by government are some of the reasons why there is a renewed interest in this sector especially by private sector players. This study, which is focused on Indian cold chain logistics, analyzes the industry on PEST (Political, Economy, Social and Technology) model and presents top 3 factors on each of these 4 parameters.

scholarly journals Optimisation of energy consumption of a solar-electric dryer during hot air drying of tomato slices

2019 ◽  
Vol 50 (3) ◽  
pp. 150-158 ◽  
Author(s):  
Nnaemeka R. Nwakuba
Keyword(s):  
Energy Consumption ◽  
Air Temperature ◽  
High Energy ◽  
Slice Thickness ◽  
Air Velocity ◽  
Hot Air Drying ◽  
Air Drying ◽  
Hot Air ◽  
Drying Conditions ◽  
Desirability Index

High-energy demand of convective crop dryers has prompted study on optimisation of dryer energy consumption for optimal and cost effective drying operation. This paper presents response surface optimisation of energy consumption of a solar-electric dryer during hot air drying of tomato slices. Drying experiments were conducted with 1 kg batch of tomato samples using a 33 central composite design of Design Expert 7.0 Statistical Package. Three levels of air velocity (1.0, 1.5 and 2.0 ms–1), slice thickness (10, 15 and 20 mm) and air temperature (50, 60 and 70°C) were used to investigate their effects on energy consumption. A quadratic model was obtained with a high coefficient of determination (R2) of 0.9825. The model was validated using the statistical analysis of the experimental parameters and normal probability plot of the energy consumption residuals. Results obtained indicate that the process parameters had significant quadratic effects (P<0.05) on the energy consumption. The energy consumption varied between 5.42 kWh and 99.78 kWh; whereas the specific energy consumption varied between 5.53 kWhkg–1 and 150.61 kWhkg–1. The desirability index method was applied in predicting the ideal energy consumption and drying conditions for tomato slices in a solar-electric dryer. At optimum drying conditions of 1.94 ms–1 air velocity, 10.36 mm slice thickness and 68.4°C drying air temperature, the corresponding energy consumption was 5.6 8kWh for maximum desirability index of 0.989. Thermal utilisation efficiency (TUE) of the sliced tomato samples ranged between 15 ≤TUE ≤58%. The maximum TUE value was obtained at 70°C air temperature, 1.0 ms–1 air velocity and 10 mm slice thickness treatment combination, whereas the minimum TUE was obtained at 50°C air temperature, 2.0 ms–1 air velocity and 20 mm slice thickness. Recommendation and prospect for further improvement of the dryer system were stated.

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