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Drying of Agro Products
Published in B. K. Bala, Agro-Product Processing Technology, 2020
Thin-layer drying experiments under controlled conditions of drying air temperature, relative humidity, and air velocity are conducted to assess their effects on drying performance and quality of the dried products such as milling quality, germination capacity, color, and nutritional status. Higher is the drying air temperature, the higher is the drying rate, and the higher the relative humidity results in lower the drying rate. The drying rate increases with air velocity, but it becomes independent of air velocity above a certain air velocity such as 0.50 m/s for hybrid rice. Figure 5.4 shows the effect of drying air temperature on drying characteristics of rice and wheat, and it shows the drying rate increases with the increase in drying air temperature. Figure 5.5 shows the germination percentage as a function of drying temperature, and it shows that germination percentage decreases with the increase in drying air temperature exponentially. Figure 5.4 suggests that drying should not be conducted at a higher temperature, but if the rice is intended to be used for seed it should not exceed 40°C. Thus, optimum temperature for drying of rice seed should be 40°C, considering both drying performance and germination percentage. But for consumption, head-rice yield, nutritional status, and temperature are important to consider. Several thin-layer drying models have been fitted to experimental data of thin-layer drying experiments conducted under control conditions of drying air temperature and relative humidity. Some selected thin-layer drying models are shown in Table 5.1.
Mold: Potential Threats Sprout in a Watery World
Published in Ed Bas, Indoor Air Quality, 2020
To have mold, you need water, or at least high humidity. The ability of air to hold water vapor decreases as the air temperature is lowered. If a unit of air contains half of the water vapor it can hold, it is said to be at 50% relative humidity (RH). As the air cools, the relative humidity increases. If the air contains all of the water vapor it can hold, it is at 100% RH, and the water vapor condenses, changing from a gas to a liquid. It is possible to reach 100% RH without changing the amount of water vapor in the air (its “vapor pressure” or “absolute humidity”). All that is required is for the air temperature to drop to the “dew point.”
Thermal Comfort
Published in Neha Gupta, Gopal Nath Tiwari, Photovoltaic Thermal Passive House System, 2022
The recommended air temperature for thermal comfort is 20°C. There is variation in ambient temperature during the day due to the change in the solar insolation levels. Also, ambient temperature is different for all months and varies from season to season. For example, the ambient temperature varies from 5°C–15°C and 30°C–45°C in the winter and summer months, respectively, for northern climatic conditions. Thus, the heating and cooling demand of the building depends on the time and season of the year.
Experimental investigation on novel heat pump system for combined drying and air conditioning for arid climate
Published in Drying Technology, 2022
Akhilesh Singh, Jahar Sarkar, Rashmi Rekha Sahoo
Figure 3 represents the variation of the evaporator outlet air temperature (cooling air temperature) with different evaporator inlet air temperatures and air flow rate for fixed condenser inlet condition and air flow rate. The cooling air temperature is higher or air temperature drop is lower for the higher mass flow rate of the air through the evaporator for the same inlet air temperature due to increase in heat capacity rate and also the cooling air temperature increases with inlet atmospheric temperature at a fixed flow rate. The evaporator output air temperature is lower for the lower mass flow rate of air due to reduced heat capacity rate and found to be in the comfort zone (temperature varies between 22 and 27 °C, relative humidity between 40 and 60%) of cooling for the highest outside atmospheric temperature of 45 °C in the current combined HP drying and air conditioning system.
Evaluation of the electrical integrity of E-textiles subjected to environmental conditions
Published in The Journal of The Textile Institute, 2018
Kelly Bogan, Abdel-Fattah M. Seyam, Jeremiah Slade
The electrical resistance of an e-textile is determined both by the properties of the material and the dimensions of the specimen. A main environmental effect on resistance is temperature. Air temperature is a measure of how hot or cold the air is. More specifically temperature describes the kinetic energy, or energy of motion, of the gasses that make up air. As gas molecules move more quickly, air temperature increases. Air temperature can affect the conductive yarn because as air temperature increases the conductive yarn will become hot, which increases resistance (Cirolia & Finan, 2001). As air temperature increases, the atoms that make up the lattice structure of conductors start to vibrate more vigorously over greater distances. As a result, mobile electrons in the conductor may collide more often with the vibrating ions, therefore causing an increase in electrical resistance (Cirolia & Finan, 2001). All materials do not react to temperature to the same degree. Temperature coefficients are expressed as the relative increase in resistance for one-degree increase in temperature. For pure metals, this coefficient is a positive number, meaning that resistance increases with increasing temperature. For the elements carbon, silicon, and germanium, this coefficient is a negative number. For some metal alloys, the temperature coefficient of resistance is very close to zero, meaning that the resistance hardly changes at all with variations in temperature (Hearle, 1953).
Enhancement of Performance and Energy Efficiency of Air Conditioning System Using Evaporatively Cooled Condensers
Published in Heat Transfer Engineering, 2019
Theodore A. Ndukaife, A. G. Agwu Nnanna
Figure 9 shows that there is a greater percentage increase in COP at higher temperatures, compared to lower temperatures. This is also noticeable by comparing the margin at different temperatures of each of the evaporative cooling case with that of the air-cooled base line, shown in Figure 8. The maximum percentage increase obtained was 44%, 35%, and 27% for the 15-cm, 10-cm, and 5-cm pad, respectively. Evaporative cooling and greater enhancement in COP is favored at higher temperatures because of the increase in the evaporation rate; this causes a greater drop in air temperature. However, at lower incoming air temperature, evaporation rate is decreased, and in such case, the usefulness of evaporative cooling is greatly diminished.