Maximum Temperature Reduction Research Articles

Recovery and effective utilization of waste heat from the exhaust of internal combustion engines for cooling applications using ANSYS

The exhaust gases from an internal combustion (IC) engine carry away about 75% of the heat energy which means only 25% of heat energy is operated for power production. A recovery unit at the exhaust outlet port can ensure heat exchange between different temperature fluids through conjugate heat transfer phenomena. This study represents heat recovery from exhaust gases that are emitted from IC engines which can be utilized in various applications such as vapor absorption refrigeration systems. In the present work, a new type of perforated fin heat exchanger for waste heat recovery of exhaust gases is designed using SolidWorks, and the flow field design of the heat recovery system is optimized using ANSYS software. Various parameters (velocity, pressure, temperature, and heat conduction) of hot and cold fluid have been analyzed. Inlet velocity of cold fluids including refrigerant (LiBr solution), water, and graphene oxide (GO) nanofluid have been adopted at 0.03 m/s, 0.165 m/s, and 0.3 m/s, respectively. Inlet velocity of hot fluid is taken as 2 m/s, 4 m/s, and 6 m/s, respectively, to develop a test matrix. The results showed that maximum temperature reduction by the exhaust is achieved at 104.8°C using graphene oxide nanofluids with an inlet velocity of 0.3 m/s and exit velocity of 2 m/s in the heat recovery unit. Similarly, temperature reduction by exhaust gases is acquired at 102 °C using water and 96.34 °C by using a refrigerant (LiBr solution) with the same exit velocity (2 m/ s). Furthermore, maximum effectiveness of 0.489 is also obtained for GO nanofluid when compared with water and the refrigerant. On the other hand, the refrigerant has the maximum log mean temperature difference from all fluids with a value of 224.4 followed by water and GO.

Highly suppressed solar absorption in a daytime radiative cooler designed by genetic algorithm

Abstract Here, we report a selective multilayer emitter for eco-friendly daytime passive radiative cooling. The types of materials and thickness of up to 10 layers of the multilayer structure are optimized by a genetic algorithm. The passive radiative cooler is designed to mainly target low solar absorption, which allows sub-ambient cooling under direct sunlight. We used a custom objective function in the solar region to achieve high-performance daytime radiative cooling to minimize solar absorption. The designed structure minimizes solar absorption with an average absorptivity of 5.0% in the solar region (0.3–2.5 μm) while strongly emitting thermal radiation with an average emissivity of 86.0% in the atmospheric transparency window (8–13 μm). The designed and fabricated structure achieves daytime net cooling flux of 84.8 W m−2 and 70.6 W m−2, respectively, under the direct AM 1.5 solar irradiation (SI) (total heat flux of 892 W m−2 in the 0.3–2.5 μm wavelength region). Finally, we experimentally demonstrate a passive radiative cooling of the fabricated selective emitter through a 72-hour day-night cycle, showing an average and maximum temperature reduction of 3.1 °C and 6.0 °C, respectively. Our approach provides additional degrees of freedom by designing both materials and thickness and thereby is expected to allow high-performance daytime radiative cooling.

Retrofitting solutions for a campus building to mitigate urban heat island in a hot humid climate

In this study we examine the summer cooling effects of trees and green facades on reducing urban heat island effects. Using ENVI-met model simulations, we investigate the influence of added greenery on the surface and ambient air temperature and its role on air fluctuations in the hot humid climate of Austin, TX, at pedestrian height. Under the specific conditions considered in this model, the results show the combination of trees and green facades has a greater cooling effect. Added greenery to the building mostly impacts the building's surface temperature during the hottest hours of the day, registering a maximum surface temperature reduction of 20.33°C. Simulations also show a maximum overall potential air temperature reduction of 0.54°C, and a maximum potential air temperature cooling effect near the building of 0.91°C. Future research should be conducted to address this study's limitations. Nevertheless, these findings can provide architects, designers, planners, and policymakers with a better understanding of the many benefits trees and green facades have, and provide them with the necessary tools to implement new solutions across sectors and scales to reduce the impacts urban areas have on the environment and provide a better living for all.

A study of a low pressure ratio vapor injection scroll compressor for electric vehicles under low ambient conditions

Vapor injection technology is a promising method to improve the performance of heat pump systems on electric vehicles. In this work, an experimental study on a low pressure ratio vapor injection scroll compressor was carried out under low ambient temperature conditions. Comparative experiments were conducted for various injection pressures, compressor speeds, and evaporation temperatures. The typical flow and heat transfer characteristics were obtained and analyzed, especially the compressor volumetric efficiency and compressor efficiency. The results showed that the heating performance was improved and discharge temperature was reduced with the increasing injection pressure at a higher compressor speed and a lower evaporation temperature. The volumetric efficiency and compressor efficiency both decreased with the increasing injection pressure. The maximum heating capacity could increase by 16% and the maximum discharge temperature reduction would reach 8 °C for the vapor injection process compared with non-injection process under the evaporation temperature of -22 °C. Furthermore, a semi-empirical model with correlations of volumetric efficiency and compressor efficiency was developed. The results were validated and showed a reasonable agreement with experimental results.

Modeling impacts of super cool roofs on air temperature at pedestrian level in mesoscale and microscale climate models

Passive daytime radiative cooling is gaining increasing relevance as recent studies report that newly developed materials with very high reflectivity and emissivity could be able to effectively reduce urban heat stress, when applied as roofing material (super cool roofs). A recent microscale sensitivity study with ENVI-met modeled the impact of super cool roofs with maximum air temperature reductions of around 0.85 K at pedestrian level for an idealized model area. To verify these findings in real urban structures featuring complex building morphologies and varying meteorological conditions, we conducted climate simulations for two contrasting cities: New York City, NY, and Phoenix, AZ. (Super) cool roof's cooling impacts are compared using mesoscale and nested microscale simulations in both cities with the Weather Research and Forecasting Model (WRF) and ENVI-met, respectively. While ENVI-met predicts daytime air temperature cooling at pedestrian level of up to 0.49 K (New York) and 0.94 (Phoenix), WRF estimates maximum cooling of 2.51 K (New York) and 3.31 K (Phoenix). Despite these differences both models showed high agreement in statistical analysis of modeled pedestrian-level air temperatures and roof surface temperatures. Climatological conditions could be identified as a major driver for cooling impact differences between New York City and Phoenix.

Climate-Based Analysis for the Potential Use of Coconut Oil as Phase Change Material in Buildings

One of the most efficient measures to reduce energy consumption in buildings is using passive thermal comfort strategies. This paper shows the potential of coconut oil as a bio-based phase change material (PCM) incorporated into construction components to improve the thermal performance of buildings for several climates, due to its environmental advantages, wide availability, and economic feasibility. The thermophysical properties of coconut oil were determined through differential scanning calorimetry. Numerical simulations were conducted in ESP-r, comparing an office space with a gypsum ceiling to one with coconut oil as PCM for 12 climate types in the Köppen–Geiger classification. The results show that coconut oil is a suitable PCM for construction applications under tropical and subtropical climates. This PCM can provide year-round benefits for these climates, even though a higher melting point is needed for optimum performance during hotter months. The highest demand reduction of 32% and a maximum temperature reduction of 3.7 °C were found in Mansa, Zambia (Cwa climate). The best results occur when average outdoor temperatures are within the temperature range of phase change. The higher the diurnal temperature range, the better the results. Our findings contribute to a better understanding of coconut oil in terms of its properties and potential for application in the building sector as PCM.

Effects of annular-cooler surface-roughness on wind resistance and thermal environment in a high-speed geotechnical centrifuge chamber

Numerical simulations were performed to illustrate the influences effects of annular-cooler surface roughness on wind resistance and thermal environment in a high-speed centrifuge chamber, with the use of multi-reference-frame (MRF) method and classical roughness-modified model. In the present study, the absolute roughness height was specified in a range form 0.05 mm–2.5 mm. With respect to the clearance between rotating-arm tip and stationary-cooler surface, the relative roughness height was changed from 0.0014 to 0.07 accordingly. The results show that the flow field inside the centrifuge chamber is of highly three-dimensional feature. With the increase of surface roughness, the wind resistance is increased monotonously. With regard to the thermal environment, the maximum temperature inside the centrifuge chamber takes on a non-monotonous variation along with the surface roughness height, due to the two contrary influencing roles of surface roughness on the viscous dissipation heat generation and the heat removal capacity. In general, the use of roughed cooler-wall is a promising scheme for reducing the environmental temperature in a high-speed centrifuge chamber. Under the present research conditions, a more favorable relative roughness height is identified in term of a comprehensive factor that reflects the benefit of roughed surface on the reduction of maximum environmental temperature at the pay of aerodynamic penalty.

Multiphysics simulation optimization framework for lithium-ion battery pack design for electric vehicle applications

Large-scale commercialization of electric vehicles (EVs) seeks to develop battery systems with higher energy efficiency and improved thermal performance. Integrating simulation-based design optimization in battery development process expands the possibilities for novel design exploration. This study presents a dual-stage multiphysics simulation optimization methodology for comprehensive concept design of Lithium-ion (Li-ion) battery packs for EV applications. At the first stage, multi-objective optimization of electrochemical thermally coupled cells is performed using genetic algorithm considering the specific energy and the maximum temperature of the cells as design objectives. At the second stage, the energy efficiency and the thermal performances of each optimally designed cell are evaluated under pack operation to account for cell-to-pack interactions under realistic working scenarios. When operating at 1.5 C discharge current, the battery pack comprising optimally designed cells for which the specific energy and the maximum temperature are equally weighted delivers the highest specific energy with enhanced thermal performance. The most favorable pack design shows 8% reduction in maximum pack temperature and 16.1% reduction in module-to-module temperature variations compared to commercially available pack. The methodology for design optimization presented in this work is generic, providing valuable knowledge for future cell and pack designs that employ different chemistries and configurations.

Experimental investigations to improve the electrical efficiency of photovoltaic modules using different convection mode

Solar energy is the most frequently used renewable energy source which receives the light energy from the sun, and it transform in to electric energy with the help of photovoltaic cell as a module. The flow of electrons or electrical energy is produced by making the sunlight photons to fall on the collector. Which produce the electrical energy, but the power generation is not completely produced because due to various losses. The most commonly occurred power loss is due to heat formed under the solar panel which affects the solar panel performance. Induced electrical energy is inversely proportional to the base panel temperature. Our main scope of the work is to remove the heat, which are accumulated under the solar panel by using different convection mode. In this paper, an experimental analysis is conducted in four different convection mode for heat removal for three days from sunrise 8.00 a.m. to 5.00 p.m. for calculating the maximum current, voltage generation and maximum heat removal. Four experiments namely, without rectangular duct under free convection, with rectangular duct under free convection, with rectangular duct under forced convection and duct with L shaped barrier and forced convection are conducted for three days. The maximum voltage induced in solar panel without duct, with duct under free convection, duct under forced convection and duct under forced convection & L shaped barrier was obtained at 11:00 a.m. as 18.54 V, 19.05 V, 21.04 V and 22.56 V. Results indicate that the maximum voltage induced is significantly increased in all the modifications such as duct under free convection, duct under forced convection and duct under forced convection & L shaped barrier by 2.75%, 13.48% and 21.68% as compared to conventional solar panel without duct condition. The inclusion of duct under free convection, duct under forced convection and duct under forced convection & L shaped barrier in solar panel base limits the maximum temperature as 44℃, 41℃ and 38℃, however the maximum temperature in the solar panel base is 49℃ for solar panel without duct condition. Reduction in solar panel base maximum temperature for duct under free convection, duct under forced convection and duct under forced convection & L shaped barrier are 10.20%, 16.33% and 22.45% as compared to conventional solar panel without duct condition. The results also indicate that the induced voltage and solar panel base panel temperature for four experiments was compared and found the maximum electrical efficiency enhancement of 21.68% with duct and L shaped barrier under forced convection than conventional method and the corresponding base panel temperature reduction is 19.15% is obtained than conventional type. The proposed system significantly increased the photovoltaic panel performance and output voltage due to enhanced evaporation rate and reduction in photovoltaic panel temperature.

Thermal Design, Optimization, and Packaging of Planar Magnetic Components

This article is focused on the thermal design and three-dimensional (3-D) package optimization of planar magnetic components (PMCs), including transformers and inductors for application in an electric vehicle composite boost dc-dc converter. Each PMC comprises electrical windings in printed circuit board (PCB) form in combination with a ferrite core. Multiple features of each PMC package are thermally optimized for the proposed device configurations with given core size, core loss distribution, number of turns in the PCB winding, winding copper thickness, and winding loss distribution. These heuristically optimized features include a lower level cold plate structure with a conformal base for enhanced convective heat transfer, an upper level PMC cap structure for doubled-sided cooling through conductive heat flow to the cold plate, the implementation of functionally distributed copper thermal and electrothermal vias in the PCB winding for improved cross-plane thermal conductance, and judicious implementation of select materials at various locations and interfaces within the package. Detailed numerical modeling reveals the combined effect of this 3-D packaging strategy with a 79.3 °C and 48.5 °C maximum temperature reduction in the core and PCB winding, respectively, relative to a baseline device configuration. Select PMC experimental validation confirms the expected thermal performance of an optimized PCB design. The thermal design approach is relevant for a range of high-power-density electronics PMC packaging applications.

Performance Improvement of Thermoelectric Air Cooler System by Using Variable-Pulse Current for Building Applications

The thermoelectric air conditioning system (TE-AC) is a small, noiseless alternative to standard vapor compression refrigeration (VCR) systems. The cooling characteristics of a TE-AC system operating under two conditions, i.e., steady current and current pulses, are investigated in this study. This system consists of three thermoelectric modules, a heat sink, and an air circulation fan. The result shows that maximum temperature reduction in cooling side of TE-AC system was achieved at 6 A input current under steady state operation. The optimum performance of the TE-AC system under steady state operation depends upon the combined effect of the cooling load, Joule, Fourier, and Peltier heat. In TE-AC pulse operation, both current width and cooling load applied on the cold side of the thermoelectric module (TEMs) play an important role in achieving optimum cooling performance of the system. When normal input current operation (i.e., no current pulse) was compared to pulse-operated TE-AC system operation, it was found that pulse operation provides an additional average temperature reduction of 3–4 °C on the cold side of TEMs. Although on the hot side, it maintains a temperature in the range of 18 °C to 24 °C to reduce overshoot heat flux. The duration of operation is also important in determining pulse width and pulse amplitude. Minimum and overshoot peak temperature rises during each cycle for longer run operation. In the TE-AC system, the accumulated Joule heat during a current pulse frequently causes a temperature overshoot, which lasts much longer. As a result, the next current pulse was not released until the temperature of TE was restored to its initial value.

Experimental Investigations for Thermal Energy Management by Encapsulation of Nano -Enhanced Bio Phase Change Material in buildings

ABSTRACT Due to the enormously increasing population in metropolitan cities of India, most of the transmissions of ozone exhausting substances are expected from metropolitans, of which the building structures may contribute significantly. To limit these levels, one of the inevitable structures of the metropolitan plan is to adopt green buildings. In this regard, integration of Nano-enhanced Bio Phase Change Material (NeBPCM) in buildings is an innovative technology that has a high potential to reduce the thermal energy penetration into the buildings, The green buildings enhance the thermal comforts inside the building with energy conservation. A novel integration of NeBPCM composite is introduced to a Solid Concrete Hollow Block of size 400 mm x 200 mm x 100 mm. The experimental building of size 1 m x 1 m x 1 m is constructed to analyze the thermal effects of this phase change material (PCM) integration within the buildings. A drop in temperature is observed in PCM integrated building from 5.3°C to 1.1°C compared to that of building without PCM. The error between the measured data and numerical predictions is found to be within the range of 0.3°C and 1.6°C. The experimental investigations also revealed a reduction in maximum room temperature up to 5.3°C in the building integrated with NeBPCM vis-à-vis building without NeBPCM. Also, NeBPCM integration in building increased the temperature by 1.8°C when the outside ambient temperature averagely dropped below 23.6°C, thus improving the thermal comfort in the buildings all over the seasons. Therefore, NeBPCM integration in buildings is advantageous in terms of maintaining the room temperature to provide passive cooling of buildings with energy savings.

Sustainable passive cooling strategy for PV module: A comparative analysis

This paper presents the experimental studies of different passive cooling techniques to analyze the electrical power improvement and temperature reduction of a 50 W polycrystalline PV module. Plant cooling, greenhouse cooling, greenhouse + plant cooling, coir pith, and phase change material cooling are the various approaches are used in the analysis. The percentage of electrical power improvement and temperature of various passive cooling techniques are compared with solar modules without cooling. The maximum percentage power improvement (11.34%) was found to be in coir pith cooling with an average maximum power of 36.38 W. The maximum temperature reduction was observed to be 14 °C in case of plant cooling with a greenhouse. Considering the electrical power improvement and temperature reduction, coir cooling and plant cooling were found to be best suited for the given climatic conditions amongst all cooling techniques. The results also showed that the reduction in temperature does not always give rise to the increase in power as it was depicted in the case of greenhouse net cooling and plant cooling with greenhouse. This kind of cooling technique is best suited for agro-based countries in tropical regions.

Effect of BaO substitution for CaO on the structural and thermal properties of SiO2–B2O3–Al2O3–CaO–Na2O–P2O5 bioactive glass system used for implant coating applications

The present study replaced 3.30 and 9.00 mol.% BaO for CaO in a SiO2–B2O3–Al2O3–CaO–Na2O–P2O5 bioactive glass system used for implant coating applications. Variations of the glass structure, thermal properties, cytotoxicity, and radiopacity of glasses were studied. As demonstrated by the results, upon adding barium oxide to the glass structure, the weight density increased significantly, while a slight decrease in oxygen density was determined. Introducing barium oxide into glass composition did not cause any considerable change in the spectra of FTIR and Raman. It was demonstrated that the amount of bridging oxygen in the glass structure remained quite unaffected. The hot stage microscopy evaluations revealed further shrinkage of barium-containing frits due to lower viscosity and hence, higher viscous flow of these glasses. By substituting barium oxide for calcium oxide and increasing its concentration, the glass transition temperature (Tg) and the dilatometric softening temperature (Td) decreased, while the thermal expansion coefficient increased. Moreover, upon substituting 9 mol.% barium oxide for calcium oxide, a 30 °C reduction in maximum sintering temperature (Tms) of the glass was obtained, whereas the shrinkage rate was increased 1.7 times. It was indicated that the sintering process of barium-incorporated glasses would easily proceed without any phase crystallization. The barium-incorporated glasses exhibited more radiopacity. Additionally, no cytotoxic effect was caused by the substitution, and the Ba-containing glasses could be used for biomedical applications and implant coating as well.

Effects of vegetation covers for outdoor thermal improvement: A Case Study at Abubakar Tafawa Balewa University, Bauchi, Nigeria

Frequent increases in temperature and related consequences have been the trending phenomenon for over ten decades, with a general rise of about 0.740C. This study evaluates the effects of different percentage covers of tree canopies for outdoor thermal improvement of campus areas in Bauchi, Nigeria. Firstly, the study involves on-site measurement of existing features on the site and the climatic conditions. Secondly, performing simulation for evaluation of the plant-surface-atmosphere interactions with Envi-met Version 4.4.2. The vegetation effects were evaluated for outdoor air temperature and mean radiant temperature (MRT) reduction. It is found that the maximum air temperature reduction of 3.380C and 24.240C of MRT were achieved with up to 45% tree canopy coverage. The mean air temperature and MRT reduction of 0.630C and 4.800C were respectively achieved with the same percentage coverage of the canopies. However, it was found that the thermal reduction effects of vegetation do not apply to every hour of the day. In essence, proper planning and implementation of campus outdoor spaces is the key factor in improving its thermal conditions. Thus, adhering to the practical recommendations bring a significant improvement in ameliorating the rise in atmospheric temperature on campus outdoors.

Interactions of wakes and shock waves with two-phase air/mist cooling in a transonic gas turbine stage

A 2-D two-phase numerical simulation was conducted to investigate the effect of interactions of moving wakes and shock waves on mist cooling performance over airfoils in a transonic gas turbine stage. The two-phase flow consists of a continuous phase (i.e., air) and a dispersed phase (i.e., mist). The tracking and evaporation of the mist are simulated by using the discrete phase model (DPM). The interactions between the droplets themselves with respect to collision and breakup were simulated by using the breakup and coalescence sub-models. The motion of the rotor domain was simulated by using the linear sliding mesh technique to study the transient stator-rotor interaction. The results show that the passing unsteady wakes caused by the blade rotation press the mist toward the blade surface, providing more enhanced film cooling effectiveness. The oblique shock wave was observed downstream of the vanes passage. The lambda shock wave was observed downstream of the blades passage. Both shock waves did not exert noticeable effect on the air/mist cooling performance. Injecting a 10% mist ratio noticeably improved the cooling enhancement by obtaining a maximum temperature reduction of 200 K and an average temperature reduction of 51 K on the vane, and a maximum of 350 K reduction and an average of 24 K reduction on the blade surface under the influence of wakes and shocks. Injecting the tiny water droplets increased the total pressure losses by 0.1% on the vane and 4% on the blade compared to the air cooling case. Injecting mist has negligible effect on the formations of shocks/wakes and their corresponding behaviors.

The Effect of the Thermal Mass of the Building Envelope on Summer Overheating of Dwellings in a Temperate Climate

The main objective of this paper is to demonstrate the effectiveness of increasing the thermal capacity of a residential building by using traditional building materials to reduce the risk of its excessive overheating during intense heat waves in a temperate climate. An additional objective is to show that the use of this single passive measure significantly reduces the risk of overheating in daytime rooms, but also, though to a much lesser extent, in bedrooms. Increasing the thermal mass of the room from light to a medium heavy reduced the average maximum daily temperature by 2.2K during the first heat wave and by 2.6K during the other two heat waves. The use of very heavy construction further reduced the average maximum temperature for the heat waves analyzed by 1.4K, 1.2K and 1.7K, respectively, giving a total possible reduction in maximum daily temperatures in the range of 3.6 °C, 3.8 °C and 4.3 °C. A discussion of the influence of occupant behavior on the use of night ventilation and external blinds was carried out, finding a significant effect on the effectiveness of the use of both methods. The results of the study suggest that in temperate European countries, preserving residential construction methods with heavy envelopes and partitions could significantly reduce the risk of overheating in residential buildings over the next few decades, without the need for night ventilation or external blinds, whose effectiveness is highly dependent on individual occupant behavior.

Effectiveness of Tree Pattern in Street Canyons on Thermal Conditions and Human Comfort. Assessment of an Urban Renewal Project in Historical District in Lodz (Poland)

The implementation of adaptation strategies has become an essential activity of spatial planning departments. Passive technologies related to the introduction of natural components in the form of vegetation are used, especially in urban development plans, to mitigate the effects of climate change and thus improve the quality of citizen life. Nature-Based Solutions are of particular importance in the areas of strict city centers, where historical building structures are subject to legal protection. In this study, the authors tested the influence of high greenery on the microclimatic conditions in the areas of typical street canyons (east–west and north–south orientations). Authors included the established greenery strategy by the City Planning Department. To estimate the impact of the assumed scenarios, a CFD tool was used—the ENVI-met application, which is commonly used in the field of urban microclimatology. Studies have shown that the introduction of 10% of green area contributed to a maximum air temperature reduction of 0.80 °C (17:00) in an east–west-oriented canyon, 0.49 °C (10:00) in a north–south canyon. The scenarios, assumed by the City Planning Department, related to the introduction of a greater amount of greenery turned out to be a less effective solution. The impact of greenery on the thermal comfort felt by humans was also determined. The reduction in the PET index was a maximum of 10.80 °C (14:00) in an east–west canyon; 6.66 °C (14:00) in a canyon area with a north–south orientation. This research might constitute the foundations to a re-evaluation of the urban development plans. The outcomes can lead to taking alternative direction of city layout transformations.

Thermal performance of concrete bricks based phase change material encapsulated by various aluminium containers: An experimental study under Iraqi hot climate conditions

This study presents the experimental results of concrete bricks based macroencapsulated phase change material (PCM) in different capsule designs (circular, square and rectangular cross-sections). Eight concrete bricks (including a reference brick without PCM) are fabricated, and their thermal performance is tested under hot summer conditions of Al Amarah city, Iraq. The study considered several indicators such as the interior maximum temperature reduction (MTR), decrement factor (DF) and time lag (TL) to compared among tested bricks in addition to the thermal behaviour during melting and solidification of PCM. Results indicated that all PCM based bricks are performed better than the reference brick in which the maximum interior temperature is shaved and shifted. Moreover, the best thermal performance is reported for bricks of large PCM capsules number. Amongst others, the brick-based square cross-section PCM capsules showed the best thermal contribution where the average MTR of 1.88°C, average DF of 0.901 and average TL of 42.5 min were obtained compared with the reference brick. The study concluded that PCM capsules' heat transfer area is the main parameter that controls PCM's thermal behaviour as long as all PCM capsules have the same PCM quantity and position. Therefore, excessive encapsulation area might influence the thermal performance of concrete brick and should be specified for the efficient use of PCM storage capacity.

Modelling of vertical greenery system with selected tropical plants in urban context to appraise plant thermal performance

Different growth parameters and thermal performances of selected plant species grown on vertical system modules in urban tropical climate have been investigated under the study. Further, outdoor thermal comfort simulation has been modeled by ENVI­met 4.4.5 to investigate the applicability of selected plant species in three different tropical conditions (Colombo Sethsiripaya administrative complex, Matara urban council building and Kandy Urban council building). Sample modular vertical green living wall panels were fabricated by using timber frames (60 × 40 × 5 cm) packed with cocopeat medium with a depth of 3.8 cm. Nine plant species; such as Desmodium triflorum, Roheo spathacea, Centella asiatica, Axonopus fissifoliu, Axonopus compressus, Elusine indica, Dieffenbachiae spp, Tectaria spp, and Bigonia spp were selected for the study. Plant survival percentages, plant height and leaf area index (LAI) were recorded for 8 weeks. Thermal performances were evaluated by considering temperatures at (a) 20 cm distance in front of the green wall, (b) substrate surface of the green wall modules and (c) inside the green wall compared to (d) adjacent bare wall (Control). The highest LAI was recorded from Roheo spp (3.99) followed by Axonopus f. (3.20) and Elusine spp (2.21). Axonopus f. exhibited the highest coverage on the living wall due to high LAI (>1). The highest temperature reduction (5.06 °C) was displayed by Axonopus f. compared to the other species as it covers large extent of the wall. The simulation study of the green walls developed with Axonopus f. signified a possible maximum temperature reduction of 2.07 °C, 3.29 °C and 2.03 °C in Colombo Sethsiripaya administrative complex, Matara urban council building and Kandy urban council building, respectively. Hence, modelling vertical greening with Axonopus f. can effectively enhance the thermal performance in urban context due to their LAI values and the thermal performances.