Investigating Thermal Performance of PCM Plates for Free Cooling Applications in South Africa

2017 ◽  
Author(s):  
Daniel M. Madyira ◽  
Ranwedzi P. Mukhodobwane ◽  
Tien C. Jen
Keyword(s):  
South Africa ◽  
Thermal Comfort ◽  
Ambient Air ◽  
Heat Transfer Fluid ◽  
Air Flow Rate ◽  
Storage Medium ◽  
Ambient Temperatures ◽  
Air Temperatures ◽  
Free Cooling ◽  
Change Material

Free cooling involves using a thermal energy storage medium such as a phase change material (PCM) in order to store the ambient “cold” during the night when ambient air temperatures are lower compared to the indoor building temperatures and release this stored “cold” by using a heat transfer fluid (i.e. air) into the building during the day when higher ambient temperatures are experienced especially during the summer months. This paper assesses the free cooling potential in South Africa by using a set of Rubitherm RT25HC PCM plates. The performance of these PCM plates is assessed by benchmarking the ambient air cooled by the PCM plates during the day against the defined thermal comfort temperatures requirements. The influence of varying the air flow rate on the availability of thermal comfort temperatures at the PCM rig outlet is also studied. The results clearly show the potential of using PCM’s as a means of cooling higher ambient air temperature which is experienced in hot summer months to within thermal comfort temperatures for human occupancy in a building.

scholarly journals Photosynthetic performance of rock-colonising lichens in the Mountain Zebra National Park, South Africa

Koedoe ◽  
1993 ◽  
Vol 36 (1) ◽  
Author(s):  
Dirk Wessels ◽  
Ludger Kappen
Keyword(s):  
South Africa ◽  
Volcanic Rock ◽  
National Park ◽  
Ambient Air ◽  
Early Morning ◽  
Photosynthetic Performance ◽  
The Other ◽  
Air Temperatures ◽  
Desert Regions

The photosynthetic behaviour of endolithic andepilithic lichens characteristic of sedimentary and volcanic rock was investigated in situ in the Mountain Zebra National Park, South Africa. The park forms part of an inland semi-desert known as the Karoo, in the Cape Province. Temperatures within Balfour sandstone were monitored, the results showing that during the early morning, temperatures within the sandstone were nearly 5@C lower than ambient air temperatures. This may enhance the frequency of water condensing on the sandstone, which may be particularly important for the endoliths Leciclea aff. sarcogynoides and Sarcogyne cf. austroafricana. Maximum photosynthetic rates of the investigated species were found at temperatures between 20@C and 30@C, far higher than the recorded optimum temperatures for lichens from temperate and desert regions. Parmelia chlorea was the most productive species. Compared to the other epiliths, Peltula capensis was found to be a moderately productive species. The photosynthetic gain of Leciclea aff. sarcogynoides and Sarcogyne cf. austro-africana was low, but the photosynthetic gain of these two species still exceeded that of Acarospora sp.

scholarly journals Ambient air quality data reported at Sasol Secunda monitoring stations during COVID-19 lockdown – Mpumalanga, South Africa

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Andrew Venter ◽  
Sandra De Vos
Keyword(s):  
South Africa ◽  
Air Quality ◽  
Ambient Air ◽  
Human Behaviour ◽  
Quality Data ◽  
Ambient Air Quality ◽  
Industrial Facilities ◽  
Ambient Temperatures ◽  
Pollutant Concentrations ◽  
Monitoring Stations

Various local and international research has been published on the effects of COVID-19 lockdown on ambient air quality. In most cases, a reduction in ambient NOx and PM concentrations have been observed with varying changes in ambient SO2 levels. Secunda, located in the Highveld Priority Area in Mpumalanga, South Africa is known for its large industrial facilities utilising coal as primary feedstock. The towns of Secunda and eMbalenhle provide the majority of the workforce to Sasol and has therefore been the focus of this study. The ambient air quality in the Secunda region was assessed due to the changes in human behaviour during lockdown, familiarity with the Sasol facility and the strategic locations of ambient air quality stations.Results show a clear decrease in ambient CO, NO2 and PM concentrations, especially during the first two weeks of lockdown. Only subtle changes were observed for ambient H2S and SO2 pollutant concentrations at the ambient monitoring stations. An increasing trend in all ambient species was observed towards the end and post lockdown, in contrast to declining ambient temperatures with the onset of winter. This is also contrary to the reduction in emissions from the factory that conducted annual maintenance in the month following lockdown (phase shutdown). This article concludes that human behaviour has a material local ambient impact on CO, NO2 and PM pollutant species, while H2S concentration profiles are more directly related to the industrial complex’s levels of activity. Ambient SO2 trends did not show a similar correlation with the facility’s activities (as H2S), but a stronger correlation was observed with the diverse local and regional sources in close proximity to Secunda and eMbalenhle. The influence of better dispersion especially on a local scale, brought about by more effective emission heights, is considered material. Moreover, meteorological factors, on local air quality, has been shown to be a material contributor to observed ambient air quality levels in the study domain

Human Perception Relation between Thermal Comfort and Air Movement for Ceiling Mounted Personalized Ventilation System

2014 ◽  
Vol 935 ◽  
pp. 329-332
Author(s):  
Bin Yang ◽  
Chandra Sekhar
Keyword(s):  
Thermal Comfort ◽  
Ventilation System ◽  
Human Perception ◽  
Office Work ◽  
Pv System ◽  
Movement Perception ◽  
Ambient Temperatures ◽  
Air Movement ◽  
Air Temperatures ◽  
Personalized Ventilation

As one kind of newly developed personalized ventilation (PV) system, the relation was explored between thermal comfort and air movement perception/acceptability/preference with tropical subjects, who had become passively acclimatized to hot conditions in the course of their day-to-day life. The tests were conducted in field environmental chamber (FEC) of National University of Singapore. 32 subjects (16 males and 16 females), performed normal office work, can choose to expose to four different PV airflow rates (4, 8, 12, 16 L/s) so as to simulating individual control. Ambient temperatures of 26°C and 23.5 °C and PV air temperatures of 26 °C, 23.5 °C and 21 °C were utilized to conduct parametric variation studies. Each combination was maintained for 15 minutes during which the subjects responded to computer-administered questionnaires. Under different PV airflow rates and ambient/PV temperature combinations, the relation between thermal comfort and air movement perception/acceptability/preference was analyzed.

scholarly journals DETERMINATION OF LOAD DURATION CURVE (ROSSANDER GRAPH) FOR THE REGIONS OF UKRAINE

2018 ◽  
Vol 40 (4) ◽  
pp. 41-49
Author(s):  
V.G. Kramar
Keyword(s):  
Thermal Load ◽  
Energy Production ◽  
Ambient Air ◽  
Heat Energy ◽  
Climatic Data ◽  
Load Duration ◽  
Ambient Temperatures ◽  
Load Duration Curve ◽  
Air Temperatures ◽  
Regional Centers

The purpose of this work is to determine the duration of the ambient air temperatures of different gradations during heating periods in different regions of Ukraine, based on the climatic data for 2005-2018 and the construction of load duration curves for the respective regions. The load duration curve (Rossander graph) is used to determine the number of maximum thermal load using hours, as well as in cases where the thermal load is provided by several sources - to determine their level of participation in the total annual heat energy production. It is important for a more accurate technical and economic evaluation of implementation results for some thermal energy sources. The climatic data of meteorological stations located in the regional centers of Ukraine and the capital of Autonomous Republic of Crimea, or as close as possible to them, were used for the study. The climatic data of heating periods from the autumn of 2005 to 2018 were considered. As the result of study, the duration of various degrees of ambient air temperature in the heating period was determined for all the regional centers of Ukraine. Taking into account the significant climatic differences in the regions of Ukraine, the results were analyzed separately for two groups of regions, for which, according to averaged data, load duration curves were determined. The examples of using of obtained results for calculations are given. On the basis of obtained data regarding duration of ambient temperatures higher than +8°C during the heating season, the energy saving potential of implementation of weather-dependent regulation of heat energy production for heating purposes in different regions was theoretically estimated, which is, on average, 8.4% for the first temperature zone (north, center) and 13% for the second zone (south).

Numerical Investigations of Outward Solidification in Cylindrical PCM Storage Unit

2015 ◽  
Vol 787 ◽  
pp. 177-181
Author(s):  
V. Antony Aroul Raj ◽  
C. Hariharan ◽  
R. Velraj ◽  
R.V. Seeniraj
Keyword(s):  
Ambient Air ◽  
Energy System ◽  
Night Time ◽  
Storage Unit ◽  
Cold Energy ◽  
Free Cooling ◽  
Implicit Finite Difference ◽  
Time Required ◽  
System Variables ◽  
Change Material

In the present work a transient numerical model is developed to investigate and predict the performance of a paraffin phase change material (PCM) in the annular portion of the cylindrical container during its solidification and melting processes. Enthalpy method of modeling is adopted and the discretised non-dimensional form of governing equations and boundary conditions are solved by implicit finite difference method by using MATLAB software. The temperature variation of PCM along two axes of the polar co-ordinates (r, z) and the time required for solidification are analyzed and presented. The effect of system variables on the performance of the Latent Heat Thermal Energy system ( LHTES) is studied. The model tested finds application in the concept of free cooling which is the process of storing the coldness of the night time ambient air in the LHTES in order to cool the building during the daytime by retrieving the stored cold energy.

TEMPERATURE MODIFICATION BY BAGS OF THE BAGWORM THYRIDOPTERYX EPHEMERAEFORMIS (LEPIDOPTERA: PSYCHIDAE)

1983 ◽  
Vol 115 (7) ◽  
pp. 855-858 ◽  
Author(s):  
P. Barbosa ◽  
M. G. Waldvogel ◽  
N. L. Breisch
Keyword(s):  
Tree Species ◽  
Internal Surface ◽  
Ambient Air ◽  
Host Tree ◽  
Ambient Temperatures ◽  
Surface Temperatures ◽  
Temperature Modification ◽  
Air Temperatures ◽  
Host Tree Species ◽  
Sun And Shade

AbstractSurface and internal temperatures of bags made by Thyridopteryx ephemeraeformis (Haworth) as well as ambient temperatures were recorded in sun and shade. Temperatures of bags in both shaded and exposed areas of the tree were significantly higher than ambient air temperatures. Bag surface temperatures were not significantly different from internal bag temperatures. Differences between internal, surface, and ambient temperatures could not be attributed to host tree species. Finally, there were no significant differences in temperature between bags with and without larvae.

scholarly journals A New Submersion Detection Sensor Using Two Resistance Temperature Detectors Operating on the Thermal Equilibrium Principle

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4310 ◽  
Author(s):  
Youngjun Lee ◽  
Young Sam Lee
Keyword(s):  
Temperature Difference ◽  
Thermal Equilibrium ◽  
Dynamic Performance ◽  
Convective Heat Transfer Coefficient ◽  
Ambient Air ◽  
Ambient Temperatures ◽  
Air Temperatures ◽  
Static Performance ◽  
Signal Conditioning Circuit ◽  
Reference Sensor

In this study, a new submersion detection sensor with improved reliability and stability is proposed. The new sensor uses two Resistance Temperature Detectors (RTDs) and operates on the thermal equilibrium principle. The submersion detection sensor controls two RTDs that maintain a constant temperature difference between them in the surrounding environment. The first RTD is used as a reference sensor to measure ambient temperature and the second RTD is supplied with higher current than the reference sensor for self-heating. When submerged, because the thermal conductivity and convective heat transfer coefficient of water are higher than that of air, the temperature difference between the two RTDs is lower in water than in air based on the thermal equilibrium principle. Under these conditions, a submersion detector with a signal conditioning circuit detects these temperature differences. The static performance of the proposed sensor was evaluated by checking whether malfunctions occurred at varying ambient temperatures, differing humidities, and when there was rainfall. In addition, the dynamic performance was evaluated using the response time at varying ambient air temperatures before submersion and with changing water temperatures after submersion, as a metric. The proposed submersion detection sensor is expected to find useful application in aircrafts, ships, and various other industrial fields.

NUMERICAL STUDY OF A SOLAR GREENHOUSE DRYER WITH A PHASE-CHANGE MATERIAL AS AN ENERGY STORAGE MEDIUM

2018 ◽  
Vol 49 (6) ◽  
pp. 509-528 ◽  
Author(s):  
Orawan Aumporn ◽  
Belkacem Zeghmati ◽  
Xavier Chesneau ◽  
Serm Janjai
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Numerical Study ◽  
Storage Medium ◽  
Solar Greenhouse ◽  
Change Material

Experimental Study on Thermal Characteristics of Finned Coil LHSU Using Paraffin as Phase Change Material

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Guansheng Chen ◽  
Nanshuo Li ◽  
Huanhuan Xiang ◽  
Fan Li
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Phase Change ◽  
Phase Change Material ◽  
Water Flow ◽  
Water Flow Rate ◽  
Thermal Characteristics ◽  
Heat Transfer Fluid ◽  
Latent Heat Storage ◽  
Change Material

It is well known that attaching fins on the tubes surfaces can enhance the heat transfer into and out from the phase change materials (PCMs). This paper presents the results of an experimental study on the thermal characteristics of finned coil latent heat storage unit (LHSU) using paraffin as the phase change material (PCM). The paraffin LHSU is a rectangular cube consists of continuous horizontal multibended tubes attached vertical fins at the pitches of 2.5, 5.0, and 7.5 mm that creates the heat transfer surface. The shell side along with the space around the tubes and fins is filled with the material RT54 allocated to store energy of water, which flows inside the tubes as heat transfer fluid (HTF). The measurement is carried out under four different water flow rates: 1.01, 1.30, 1.50, and 1.70 L/min in the charging and discharging process, respectively. The temperature of paraffin and water, charging and discharging wattage, and heat transfer coefficient are plotted in relation to the working time and water flow rate.

scholarly journals Barriers on Establishing Passive Strategies in Office Spaces: A Case Study in a Historic University Building

2021 ◽  
Vol 13 (8) ◽  
pp. 4563
Author(s):  
Nuno Baía Baía Saraiva ◽  
Luisa Dias Dias Pereira ◽  
Adélio Rodrigues Gaspar ◽  
José Joaquim da Costa
Keyword(s):  
Thermal Comfort ◽  
Indoor Environment ◽  
Hvac Systems ◽  
Heritage Buildings ◽  
Full Capacity ◽  
Free Cooling ◽  
Passive Strategies ◽  
The University ◽  
Indoor Conditions

The adaptation of spaces to different usage typologies can be complex in heritage buildings. Facilities were initially planned for a specific type of use that, when changed, require additional measures to ensure a suitable indoor environment. Passive strategies—e.g., free cooling—are commonly used as an alternative without requiring equipment installation. However, its implementation often leads to unsatisfactory conditions. Therefore, it is important to clarify the main barriers to achieving thermal comfort in readapted historic buildings. The present work investigates the thermal comfort conditions reported by workers in office spaces of a historic building in the University of Coimbra. A monitoring campaign was carried out between May and September 2020 to assess indoor conditions’ quality. Due to the current pandemic of COVID-19, offices were not occupied at full capacity. A one-day evaluation of thermal comfort was made using a climate analyzer and six occupants were surveyed on 19 August 2020. The main results highlighted discomfort due to overheating of spaces. The causes were related to the combination of inadequate implementation of the free cooling actions and the building use. Furthermore, it was recommended the installation of HVAC systems in case of full capacity.

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