Influences of ambient air speed and internal heat load on the performance of solar chimney in the tropics

Solar Energy ◽  
2014 ◽  
Vol 102 ◽  
pp. 116-125 ◽  
Author(s):  
Alex Yong Kwang Tan ◽  
Nyuk Hien Wong
Keyword(s):  
Heat Load ◽  
Internal Heat ◽  
Ambient Air ◽  
Solar Chimney ◽  
Air Speed ◽  
The Tropics

Thermoregulation of juvenile grey seals, Halichoerus grypus, in air

1996 ◽  
Vol 74 (2) ◽  
pp. 201-208 ◽  
Author(s):  
Patrice Boily ◽  
David M. Lavigne
Keyword(s):  
Metabolic Rate ◽  
Core Temperature ◽  
Low Temperatures ◽  
Heat Load ◽  
Cold Water ◽  
Internal Heat ◽  
Ambient Air ◽  
Halichoerus Grypus ◽  
Metabolic Depression ◽  
Air Temperatures

Metabolic rate, core temperature, and duration of sleep-related apnea events were monitored in three juvenile grey seals (Halichoerus grypus) aged 7–19 months (49–78 kg), at ambient air temperatures ranging from −18 °C to 35 °C. At low temperatures, only one seal increased its metabolic rate (at −18 °C), whereas at high temperatures (up to 35 °C) none of the three animals increased its metabolic rate. Nonetheless, seals usually became hyperthermic when they were subjected to air temperatures of 30 °C or higher. There was no indication that the duration of sleep-related apnea was greater at higher temperatures. The sleeping metabolic rate was significantly lower (20%) than the resting level. A metabolic depression associated with sleep may be advantageous at higher temperatures, reducing the internal heat load of the animal. These results suggest that cold-water adaptations of juvenile grey seals do not interfere with their ability to cope with higher air temperatures. Also, such animals should not be directly limited in their distribution by either high or low ambient air temperatures.

Small and Full-Scale Modeling for the Application of Wall Solar Chimneys

2016 ◽  
Author(s):  
David Park ◽  
Francine Battaglia
Keyword(s):  
Natural Ventilation ◽  
Velocity Ratio ◽  
Thermal Conditions ◽  
Ambient Air ◽  
Full Scale ◽  
Scale Model ◽  
Small Scale ◽  
Solar Chimney ◽  
Window Position ◽  
Pi Theorem

A solar chimney is a natural ventilation technique that has a potential to save energy consumption as well as to maintain the air quality in the building. However, studies of buildings are often challenging due to their large sizes. The objective of the current study was to determine relationships between small- and full-scale solar chimney system models. In the current work, computational fluid dynamics (CFD) was utilized to model different building sizes with a solar chimney system, where the computational model was validated with the experimental study of Mathur et al. The window, which controls entrainment of ambient air, was also studied to determine the effects of window position. Correlations for average velocity ratio and non-dimensional temperature were consistent regardless of window position. Buckingham pi theorem was employed to further non-dimensionalize the important variables. Regression analysis was conducted to develop a mathematical model to predict a relationship among all of the variables, where the model agreed well with simulation results with an error of 2.33%. The study demonstrated that the flow and thermal conditions in larger buildings can be predicted from the small-scale model.

Development of a Predictive Equation for Ventilation in a Wall-Solar Chimney System

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
David Park ◽  
Francine Battaglia
Keyword(s):  
Mathematical Model ◽  
Relative Error ◽  
Natural Ventilation ◽  
Thermal Conditions ◽  
Ambient Air ◽  
Maximum Error ◽  
Scale Model ◽  
Small Scale ◽  
Maximum Relative Error ◽  
Solar Chimney

A solar chimney is a natural ventilation technique that has potential to save energy consumption as well as to maintain the air quality in a building. However, studies of buildings are often challenging due to their large sizes. The objective of this study was to determine the relationships between small- and full-scale solar chimney system models. Computational fluid dynamics (CFD) was employed to model different building sizes with a wall-solar chimney utilizing a validated model. The window, which controls entrainment of ambient air for ventilation, was also studied to determine the effects of window position. A set of nondimensional parameters were identified to describe the important features of the chimney configuration, window configuration, temperature changes, and solar radiation. Regression analysis was employed to develop a mathematical model to predict velocity and air changes per hour, where the model agreed well with CFD results yielding a maximum relative error of 1.2% and with experiments for a maximum error of 3.1%. Additional wall-solar chimney data were tested using the mathematical model based on random conditions (e.g., geometry, solar intensity), and the overall relative error was less than 6%. The study demonstrated that the flow and thermal conditions in larger buildings can be predicted from the small-scale model, and that the newly developed mathematical equation can be used to predict ventilation conditions for a wall-solar chimney.

Modeling the Applicability of a Displacement Ventilation System

2021 ◽  
Vol 11 (1) ◽  
pp. 63-89
Author(s):  
Edgar C. Ambos ◽  
Evan Neil V. Ambos ◽  
Lanndon A. Ocampo
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Heat Load ◽  
Ventilation System ◽  
Internal Heat ◽  
The Philippines ◽  
Airflow Rate ◽  
Displacement Ventilation ◽  
Tropical Country

Due to its significant role in improving indoor air quality, displacement ventilation system is widely adopted in current literature. This paper proposes a displacement ventilation system for room conditions with ceilings that are relatively low, internal heat load could be high, walls could be sunlit, and occupants doing the low physical activity. These conditions are prevalent in the Philippines, being a tropical country. Input parameters to the design process such as heat load, the height of the ceiling, comfort, and indoor air quality requirements were generated, and the main output parameters are the stratification height and ventilation airflow rate. To demonstrate the proposed displacement ventilation system, four cases were generated. Results show that the ventilation airflow rates obtained from the four cases were greater than the minimum outdoor air requirements for health in conference rooms and large assembly areas which are 17.5 and 3.5 liters/sec*person respectively, for smoking and no smoking rooms.

Effects of hypoxia on thermal polypnea in intact and carotid body-denervated conscious cats

1989 ◽  
Vol 67 (2) ◽  
pp. 578-583 ◽  
Author(s):  
M. Bonora ◽  
H. Gautier
Keyword(s):  
Body Temperature ◽  
Carotid Body ◽  
Heat Load ◽  
Heat Exposure ◽  
Ambient Air ◽  
Severe Hypoxia ◽  
Central Action ◽  
Lower Body ◽  
Respiratory Response ◽  
Mild Hypoxia

The effects of the level of oxygenation on the respiratory response to heat exposure have been studied in conscious cats during normoxia, severe or mild hypocapnic hypoxia [inspired O2 fraction (FIO2) = 0.11 or 0.13], or hyperoxia. Several cats were also studied during severe normocapnic hypoxia. Experiments were repeated while the same animals were chronically carotid body denervated (CBD). The increase in respiratory frequency (f) leading to thermal tachypnea occurred at a lower body temperature (Tb) in severe hypocapnic hypoxia than in ambient air, but this effect was less pronounced when hypocapnia was corrected. No significant changes were observed during mild hypoxia or hyperoxia compared with normoxia in intact animals. After CBD, thermal tachypnea occurred at lower Tb in air than it did with intact animals in three of five cats, and it also occurred at lower Tb in mild hypocapnic hypoxia compared with air. It appears, therefore, that in conscious cats exposed to heat load 1) severe hypoxia enhances thermal tachypnea, 2) this effect persists after CBD, which suggests that it originates from a central action of hypoxia, and 3) the chemoreceptor afferents, to some degree, inhibit the onset of thermal tachypnea, as was previously observed for hypoxic tachypnea, which appears only in CBD cats (J. Appl. Physiol. 49: 769–777, 1980). Therefore, triggering of thermal and hypoxic tachypnea may involve common central mechanisms, probably located in the diencephalic structures under the control of afferents from arterial chemoreceptors.

Heat and Mass Transfer Analysis of a Pot-in-Pot Refrigerator Using Reynolds Flow Model

2016 ◽  
Vol 8 (3) ◽  
Author(s):  
Ramendra Pandey ◽  
Bala Pesala
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Ambient Temperature ◽  
Heat And Mass Transfer ◽  
Heat Load ◽  
Radiation Heat Transfer ◽  
Ambient Air ◽  
Total Heat ◽  
Maximum Efficiency ◽  
Radiation Heat

Heat and mass transfer analysis of evaporative cooling process in a pot-in-pot cooling system is done based on Reynolds flow hypotheses. The model proposed herein assumes that the heat transfer due to natural convection is coupled with an imaginary ambient air mass flow rate (gAo) which is an essential assumption in order to arrive at the solution for the rate of water evaporation. Effect of several parameters on the pot-in-pot system performance has been studied. The equations are iteratively solved and detailed results are presented to evaluate the cooling performance with respect to various parameters: ambient temperature, relative humidity (RH), pot height, pot radius, total heat load, thermal and hydraulic conductivity, and radiation heat transfer. It was found that pot height, pot radius, total heat load, and radiation heat transfer play a critical role in the performance of the system. The model predicts that at an ambient temperature of 50 °C and RH of 40%, the system achieves a maximum efficiency of 73.44% resulting in a temperature difference of nearly 20 °C. Similarly, for a temperature of 30 °C and RH of 80%, the system efficiency was minimum at 14.79%, thereby verifying the usual concept that the pot-in-pot system is best suited for hot and dry ambient conditions.

scholarly journals МЕТОДОЛОГИЧЕСКИЙ ПОДХОД К ЭНЕРГОСБЕРЕГАЮЩЕМУ ХЛАДОСНАБЖЕНИЮ СИСТЕМ КОНДИЦИОНИРОВАНИЯ ВОЗДУХА АДАПТАЦИЕЙ К ТЕКУЩИМ КЛИМАТИЧЕСКИМ УСЛОВИЯМ

2018 ◽  
pp. 58-62
Author(s):  
Євген Іванович Трушляков
Keyword(s):  
Heat Load ◽  
Methodological Approach ◽  
Ambient Air ◽  
High Energy ◽  
Climatic Conditions ◽  
Refrigeration Capacity ◽  
The Difference ◽  
Heat Loads ◽  
Refrigeration Machine ◽  
Current Heat

The methodological approach was suggested to define a rational heat load of the air conditioning system (ACS) with taking into consideration the current climatic conditions of operation. The proposed approach is based on the hypothesis of sharing the current changeable heat load on the relatively stable share as the basic one for choosing installed (designed) refrigeration capacity of the refrigeration machine, operating with high energy efficiency in nominal or similar modes, and unstable heat load, corresponding to ambient air precooling at changeable current temperatures. To prove the methodological approach to defining a rational heat load of the ACS was carried out the analysis of current values of heat loads of the refrigeration machine ACS during cooling ambient air from its changeable current temperature to the temperature of 10, 15 and 20 ºС . It is shown that due to the different rates of annular refrigeration capacity production increment to cover the current heat loads with increasing the installed refrigeration capacity of the refrigeration machine, caused by the changes in heat load according to current climatic conditions during all the year round, it is necessary to choose a such heat load on the refrigeration machine of ACS (its installed refrigeration capacity), that provides a maximum or similar annular refrigeration capacity production at relatively high rates of its increment. Therein, the value of heat load for ambient air precooling is calculated according to remained principle as the difference between the rational total heat load and its basic relatively stable share. The proposed method is useful for defining a basic installed refrigeration capacity of the refrigeration machine of ACS with the accumulation of excessive (unapplied) refrigeration capacity at lowered current heat loads on ACS and its application for ambient air precooling, that is for covering unstable heat load share on ACS

Sign in / Sign up

Export Citation Format

Share Document