Abstract: Several meteorological parameters were used for the
prediction of monthly average daily global solar radiation on
horizontal using recurrent neural networks (RNNs). Climatological
data and measures, mainly air temperature, humidity, sunshine
duration, and wind speed between 1995 and 2007 were used to design
and validate a feed forward and recurrent neural network based
prediction systems. In this paper we present our reference system
based on a feed-forward multilayer perceptron (MLP) as well as the
proposed approach based on an RNN model. The obtained results
were promising and comparable to those obtained by other existing
empirical and neural models. The experimental results showed the
advantage of RNNs over simple MLPs when we deal with time series
solar radiation predictions based on daily climatological data.
Abstract: A numerical investigation of the fin efficiency and temperature distribution of an annular fin under dehumidification has been presented in this paper. The non-homogeneous second order differential equation that describes the temperature distribution from the fin base to the fin tip has been solved using the central finite difference method. The effects of variations in parameters including relative humidity, air temperature, air face velocity on temperature distribution and fin efficiency are investigated and compared with those under fully dry fin conditions. Also, the effect of fin pitch on the dimensionless temperature has been studied.
Abstract: Understanding the behavior of airflow in a room is essential for building designers to provide the most efficient design of ventilation system, and having acceptable indoor air quality. This trend is the motive to solve the relationship between airflow parameters and thermal comfort. This paper investigates airflow characteristics, indoor air quality (IAQ), and the thermal comfort (TC) in a ventilated room with a displacement ventilation system using three dimensional CFD code [AirPak 2.0.6]. After validation of the code, a numerical study is executed for a typical room with dimensions of 5m by 3m by 3m height according to a variety of supply air velocities, supply air temperature and supply air relative humidity. The finite volume method and the indoor zero equation turbulence models are employed for solving the governing equations numerically. The temperature field and the mean age of air (MAA) in the modeled room for a displacement ventilation system are determined according to a variety of the above parameters. The variable air volume (VAV) systems with different supply air velocity are applicable to control room air temperature for a displacement ventilation system.
Abstract: The purpose of present work was to study the drying kinetics of whole acorn and its kernel at different drying air temperatures and their effective moisture diffusivity. The results indicated that the drying time of whole acorn was 442, 206 and 188 min at the air temperature of 65, 75 and 85ºC, respectively. At the same temperatures, the drying time of kernel was 131, 56 and 76min. The results showed that the effect of drying air temperature increasing on the drying time reduction could not be significant on acorn drying at all conditions. The effective moisture diffusivity of whole acorn and kernel increased with increasing air temperature from 65 to 75ºC. However more air temperature increasing, led to decreasing this property of acorn kernel. The critical temperature of acorn drying was about 75°C in which acorn kernel had the highest effective moisture diffusivity.
Abstract: Ascorbic acid (AA), commonly known as vitamin C, is essential for normal functioning of the body and maintenance of metabolic integrity. Among its various roles are as an antioxidant, a cofactor in collagen formation and other reactions, as well as reducing physical stress and maintenance of the immune system. Recent collaborative research between the Australian Defence Science and Technology Organisation (DSTO) in Scottsdale, Tasmania and RMIT University has sought to overcome the problems arising from the inherent instability of ascorbic acid during processing and storage of foods. The recent work has demonstrated the potential of microencapsulation by spray drying as a means to enhance retention. The purpose of this current study has been focused upon the influence of spray drying conditions on the properties of encapsulated ascorbic acid. The process was carried out according to a central composite design. Independent variables were: inlet temperature (80-120° C) and feed flow rate (7-14 mL/minute). Process yield, ascorbic acid loss, moisture content, water activity and particle size distribution were analysed as responses. The results have demonstrated the potential of microencapsulation by spray drying as a means to enhance retention. Vitamin retention, moisture content, water activity and process yield were influenced positively by inlet air temperature and negatively by feed flow rate.
Abstract: The objective of this study is to present the test
results of variable air volume (VAV) air conditioning system
optimized by two objective genetic algorithm (GA). The objective
functions are energy savings and thermal comfort. The optimal set
points for fuzzy logic controller (FLC) are the supply air temperature
(Ts), the supply duct static pressure (Ps), the chilled water
temperature (Tw), and zone temperature (Tz) that is taken as the
problem variables. Supply airflow rate and chilled water flow rate are
considered to be the constraints. The optimal set point values are
obtained from GA process and assigned into fuzzy logic controller
(FLC) in order to conserve energy and maintain thermal comfort in
real time VAV air conditioning system. A VAV air conditioning
system with FLC installed in a software laboratory has been taken for
the purpose of energy analysis. The total energy saving obtained in
VAV GA optimization system with FLC compared with constant air
volume (CAV) system is expected to achieve 31.5%. The optimal
duct static pressure obtained through Genetic fuzzy methodology
attributes to better air distribution by delivering the optimal quantity
of supply air to the conditioned space. This combination enhanced
the advantages of uniform air distribution, thermal comfort and
improved energy savings potential.
Abstract: This paper reported an experimental research of
steady-state heat transfer behaviour of a gas flowing through a fixed
bed under the different operating conditions. Studies had been carried
out in a fixed-bed packed methanol synthesis catalyst percolated by air
at appropriate flow rate. Both radial and axial direction temperature
distribution had been investigated under the different operating
conditions. The effects of operating conditions including the reactor
inlet air temperature, the heating pipe temperature and the air flow rate
on temperature distribution was investigated and the experimental
results showed that a higher inlet air temperature was conducive to
uniform temperature distribution in the fixed bed. A large temperature
drop existed at the radial direction, and the temperature drop increased
with the heating pipe temperature increasing under the experimental
conditions; the temperature profile of the vicinity of the heating pipe
was strongly affected by the heating pipe temperature. A higher air
flow rate can improve the heat transfer in the fixed bed. Based on the
thermal distribution, heat transfer models of the fixed bed could be
established, and the characteristics of the temperature distribution in
the fixed bed could be finely described, that had an important practical
significance.
Abstract: A solar powered air heating system using one ended evacuated tubes is experimentally investigated. A solar air heater containing forty evacuated tubes is used for heating purpose. The collector surface area is about 4.44 m2. The length and outer diameters of the outer glass tube and absorber tube are 1500, 47 and 37 mm, respectively. In this experimental setup, we have a header (heat exchanger) of square shape (190 mm x 190 mm). The length of header is 1500 mm. The header consists of a hollow pipe in the center whose diameter is 60 mm through which the air is made to flow. The experimental setup contains approximately 108 liters of water. Water is working as heat collecting medium which collects the solar heat falling on the tubes. This heat is delivered to the air flowing through the header pipe. This heat flow is due to natural convection and conduction. The outlet air temperature depends upon several factors along with air flow rate and solar radiation intensity. The study has been done for both up-flow and down-flow of air in header in similar weather conditions, at different flow rates. In the present investigations the study has been made to find the effect of intensity of solar radiations and flow rate of air on the out let temperature of the air with time and which flow is more efficient. The obtained results show that the system is highly effective for the heating in this region. Moreover, it has been observed that system is highly efficient for the particular flow rate of air. It was also observed that downflow configuration is more effective than up-flow condition at all flow rates due to lesser losses in down-flow. The results show that temperature differences of upper head and lower head, both of water and surface of pipes on the respective ends is lower in down-flow.
Abstract: Nowadays, the importance of energy saving is clearance to everyone. By attention to increasing price of fuels and also the problems of environment pollutions, there are the most efforts for using fuels littler and more optimum in everywhere. This essay studies optimizing of gas consumption in gas-burner space heaters. In oven of each gas-burner space heaters there is two snags to prevent the hot air (the result of combustion of natural gas) to go out of oven of the gas-burner space heaters directly without delivering its heat to the space of favorite environment like a room. These snags cause a excess circulating that helps hot air deliver its heat to the space of favorite environment. It means the exhaust air temperature will be decreased then when there are no snags. This is the aim of this essay to use maximum potential energy of the natural gas to make heat. In this study, by the help of a finite volume software (FLUENT) consumption of the gas-burner space heaters is simulated and optimized. At the end of this writing, by comparing the results of software and experimental results, it will be proved the authenticity of this method.
Abstract: A better understanding of cloud forest characteristic in a tropical montane cloud forest at Khao Nan, Nakhon Si Thammarat on climatic, vegetation, soil and hydrology were studied during 18-21 April 2007. The results showed that as air temperature at Sanyen cloud forest increased, the percent relative humidity decreased. The amount of solar radiation at Sanyen cloud forest had a positive association with the amount of solar radiation at Parah forest. The amount of solar radiation at Sanyen cloud forest was very low with a range of 0-19 W/m2. On the other hand, the amount of solar radiation at Parah forest was high with a range of 0-1000 W/m2. There was no difference between leaf width, leaf length, leaf thickness and leaf area with increasing in elevations. As the elevations increased, bush height and tree height decreased. There was no association between bush width and bush ratio with elevation. As the elevations increased, the percent epiphyte cover and the percent soil moisture increased but water temperature, conductivity, and dissolved oxygen decreased. The percent soil moistures and organic contents were higher at elevations above 900 m than elevations below.
Abstract: The 'wind-rain' house has a courtyard with glazed
roof, which allows more direct sunlight to come into indoor spaces
during the winter. The glazed roof can be partially opened or closed
and automatically controlled to provide natural ventilation in order to
adjust for indoor thermal conditions and the roof area can be shaded
by reflective insulation materials during the summer. Two field
studies for evaluating indoor thermal conditions of the two 'windrain'
houses have been carried out by author in 2009 and 2010.
Indoor and outdoor air temperature and relative humidity adjacent to
floor and ceiling of the two sample houses were continuously tested
at 15-minute intervals, 24 hours a day during the winter months.
Based on field study data, this study investigates relationships
between building design and indoor thermal condition of the 'windrain'
house to improve the future house design for building thermal
comfort and energy efficiency
Abstract: How to simulate experimentally the air flow and heat
transfer under microgravity on the ground is important, which has not
been completely solved so far. Influence of gravity on air natural
convection results in convection heat transfer on ground difference
from that on orbit. In order to obtain air temperature and velocity
deviations of manned spacecraft during terrestrial thermal test,
dimensionless number analysis and numerical simulation analysis are
performed. The calculated temperature distribution and velocity
distribution of the horizontal test cases are compared to the vertical
cases. The results show that the influence of gravity is neglected for
facility drawer racks and more obvious for vertical cabins.
Abstract: Having done in this study, air-conditioning
automation for patisserie shopwindow was designed. In the cooling
sector it is quite important to cooling up the air temperature in the
shopwindow within short time interval. Otherwise the patisseries
inside of the shopwindow will be spoilt in a few days. Additionally
the humidity is other important parameter for the patisseries kept in
shopwindow. It must be raised up to desired level in a quite short
time. Traditional patisserie shopwindows only allow controlling
temperature manually. There is no humidity control and humidity is
supplied by fans that are directed to the water at the bottom of the
shopwindows. In this study, humidity and temperature sensors
(SHT11), PIC, AC motor controller, DC motor controller, ultrasonic
nebulizer and other electronic circuit members were used to simulate
air conditioning automation for patisserie shopwindow in proteus
software package. The simulation results showed that temperature
and humidity values are adjusted in desired time duration by openloop
control technique. Outer and inner temperature and humidity
values were used for control mechanism.
Abstract: In the present study, the rate of NOx emission in a
combustion chamber working in conventional combustion and High
Temperature Air Combustion (HiTAC) system are examined using
CFD modeling. The effect of peak temperature, combustion air
temperature and oxygen concentration on NOx emission rate was
undertaken. Results show that in a fixed oxygen concentration,
increasing the preheated air temperature will increase the peak
temperature and NOx emission rate. In addition, it was observed that
the reduction of the oxygen concentration in the fixed preheated air
temperature decreases the peak temperature and NOx emission rate.
On the other hand, the results show that increase of preheated air
temperature at various oxygen concentrations increases the NOx
emission rate. However, the rate of increase in HiTAC conditions is
quite lower than the conventional combustion. The modeling results
show that the NOx emission rate in HiTAC combustion is 133% less
than that of the conventional combustion.
Abstract: Predict daily global solar radiation (GSR) based on meteorological variables, using Multi-layer perceptron (MLP) neural networks is the main objective of this study. Daily mean air temperature, relative humidity, sunshine hours, evaporation, wind speed, and soil temperature values between 2002 and 2006 for Dezful city in Iran (32° 16' N, 48° 25' E), are used in this study. The measured data between 2002 and 2005 are used to train the neural networks while the data for 214 days from 2006 are used as testing data.
Abstract: The objective of this study is to determine the thermal comfort among worker at Malaysian automotive industry. One critical manual assembly workstation had been chosen as a subject for the study. The human subjects for the study constitute operators at Body Assembly Station of the factory. The environment examined was the Relative Humidity (%), Airflow (m/s), Air Temperature (°C) and Radiant Temperature (°C) of the surrounding workstation area. The environmental factors were measured using Babuc apparatus, which is capable to measure simultaneously those mentioned environmental factors. The time series data of fluctuating level of factors were plotted to identify the significant changes of factors. Then thermal comfort of the workers were assessed by using ISO Standard 7730 Thermal sensation scale by using Predicted Mean Vote (PMV). Further Predicted percentage dissatisfied (PPD) is used to estimate the thermal comfort satisfaction of the occupant. Finally the PPD versus PMV were plotted to present the thermal comfort scenario of workers involved in related workstation. The result of PMV at the related industry is between 1.8 and 2.3, where PPD at that building is between 60% to 84%. The survey result indicated that the temperature more influenced comfort to the occupants
Abstract: Dew harvesting needs only weak investment and
exploits a free, clean and inexhaustible energy. This study aims to
measure the relative contributions of dew and rain water in the
Mediterranean Dalmatian coast and islands of Croatia and determine
whether dew water is potable. Two sites were chosen, an open site on
the coast favourable to dew formation (Zadar) and a less favourable
site in a circus of mountains in Komiža (Vis Island). Between July
1st, 2003 and October 31st, 2006, dew hasbeen daily collected on a 1
m2 tilted (30°) test dew condenser together with ordinary
meteorological data (air temperature and relative humidity, cloud
coverage, windspeed and direction). The mean yearly cumulative
dew yields were found to be 20 mm (Zadar) and 9.3 mm (Komiža ).
During the dry season (May to October), monthly cumulative dew
water yield can represent up to 38% of water collected by rain fall. In
July 2003 and 2006, dew water represented about 120% of the
monthly cumulative rain water. Dew and rain water were analyzed in
Zadar. The corresponding parameters were measured: pH, electrical
conductivity, major anions (HCO3
-, Cl-, SO4
2-
, NO3
-
, ,) and major
cations (NH4
+, Na+, K+, Ca2+, Mg2+. Both dew and rain water are in
conformity with the WHO directives for potability except Mg2+.
Using existing roofs and refurbishing the abandoned impluviums to
permit dew collection could then provide a useful supplementary
amount of water, especially during the dry season.
Abstract: Water quality and freshwater fish diversity from nine
waterfalls at Khao Luang National Park, Thailand was examined.
Streams were shallow, fast flowing with clear water and rocky and
sandy substrate. The mean water quality of waterfalls at Khao Luang
National Park were as following pH 7.50, air temperature 24.27 °C,
water temperature 26.37 °C, dissolved oxygen 7.88 mg/l, hardness
4.44-21.33 mg/l, alkalinity 3.55-11.88 mg/(as CaCO3). Twenty fish
species were found at Khao Luang National Park belonging to nine
families. A cluster analysis of water quality at Khao Luang National
Park revealed that waterfalls at Khao Luang National Park were
divided into two groups: A and B. Group A composed of two
waterfalls (i.e. Aie Kaew and Wangmaipak) that flew to the Gulf of
Thailand side. Group B composed of seven waterfalls (i.e. Promlok,
Kalom, Nuafa, Suankun, Soidaw, Suanhai, and Thapae) that flew to
the Andaman Sea side (Fig. 2) .The Cyprinids represented the major
species in all the waterfalls comprising of 45%.
Abstract: The mitigation of crop loss due to damaging freezes
requires accurate air temperature prediction models. Previous work
established that the Ward-style artificial neural network (ANN) is a
suitable tool for developing such models. The current research
focused on developing ANN models with reduced average prediction
error by increasing the number of distinct observations used in
training, adding additional input terms that describe the date of an
observation, increasing the duration of prior weather data included in
each observation, and reexamining the number of hidden nodes used
in the network. Models were created to predict air temperature at
hourly intervals from one to 12 hours ahead. Each ANN model,
consisting of a network architecture and set of associated parameters,
was evaluated by instantiating and training 30 networks and
calculating the mean absolute error (MAE) of the resulting networks
for some set of input patterns. The inclusion of seasonal input terms,
up to 24 hours of prior weather information, and a larger number of
processing nodes were some of the improvements that reduced
average prediction error compared to previous research across all
horizons. For example, the four-hour MAE of 1.40°C was 0.20°C, or
12.5%, less than the previous model. Prediction MAEs eight and 12
hours ahead improved by 0.17°C and 0.16°C, respectively,
improvements of 7.4% and 5.9% over the existing model at these
horizons. Networks instantiating the same model but with different
initial random weights often led to different prediction errors. These
results strongly suggest that ANN model developers should consider
instantiating and training multiple networks with different initial
weights to establish preferred model parameters.
Abstract: In this paper, the feasibility study of using a hybrid
system of ground heat exchangers (GHE) and direct evaporative
cooling system in arid weather condition has been performed. The
model is applied for Yazd and Kerman, two cities with arid weather
condition in Iran. The system composed of three sections: Ground-
Coupled-Circuit (GCC), Direct Evaporative Cooler (DEC) and
Cooling Coil Unite (CCU). The GCC provides the necessary precooling
for DEC. The GCC includes four vertical GHE which are
designed in series configuration. Simulation results show that
hybridization of GCC and DEC could provide comfort condition
whereas DEC alone did not. Based on the results the cooling
effectiveness of a hybrid system is more than unity. Thus, this novel
hybrid system could decrease the air temperature below the ambient
wet-bulb temperature. This environmentally clean and energy
efficient system can be considered as an alternative to the mechanical
vapor compression systems.