A Numerical Model for Thermal Performance of an Unglazed Transpired Solar Collector

2011 ◽  
Author(s):  
Saeed Moaveni ◽  
Patrick A. Tebbe ◽  
Louis Schwartzkopf ◽  
Joseph Dobmeier ◽  
Joseph Gehrke ◽  
...  
Keyword(s):  
Numerical Model ◽  
Air Temperature ◽  
Thermal Performance ◽  
Solar Collector ◽  
Energy Savings ◽  
Ambient Air ◽  
Solar Collectors ◽  
Heating Unit ◽  
Plate Temperature ◽  
Building Wall

In this paper, we will present a numerical model for estimating the thermal performance of unglazed transpired solar collectors located on the Breck School campus in Minneapolis, Minnesota. The solar collectors are installed adjacent to the southeast facing wall of a field house. The collectors preheat the intake air before entering the primary heating unit. The solar collector consists of 8 separate panels (absorber plates). Four fans are connected to the plenum that is created by the absorber plates and the adjoining field house wall. All fresh air for the field house is provided by the solar collectors before being filtered and heated by four, independent two stage natural gas fired heaters. Moreover, the following data were collected onsite using a data acquisition system: indoor field house space temperature, ambient air temperature, wind speed, wind direction, the plenum exit air temperature, the absorber plate temperature, and the air temperatures inside the plenum. The energy balance equations for the collector, the adjacent building wall, and the plenum are formulated. The numerical model is used to predict the air temperature rise inside the plenum, recaptured heat loss from the adjoining building wall, energy savings, and the efficiency of the collectors. The results of the numerical model are then compared to the results obtained from the onsite measurements; which are in good agreement. The model presented in this paper is simple yet accurate enough for architects and engineers to use it with ease to predict the thermal performance of a collector.

scholarly journals Long-Term Weather Data Measurements From A Danish Climate Station And The Weather’s Influence On The Thermal Performance Of Solar Collectors

2015 ◽  
Vol 23 (2) ◽  
pp. 23-29
Author(s):  
Lukáš Skalík
Keyword(s):  
Air Temperature ◽  
Thermal Performance ◽  
Global Radiation ◽  
Diffuse Radiation ◽  
Ambient Air ◽  
Energy Output ◽  
Weather Data ◽  
Solar Collectors ◽  
Ambient Air Temperature ◽  
Climate Station

Abstract A weather data evaluation from a climate station in Lyngby, Denmark, was carried out. Twenty years of measurements show that the increase in global radiation was almost 3.5 kWh/m2 per year, corresponding to a growth of the yearly global radiation of 7 % for the last 20 years. The global radiation variation between the least sunny year to the sunniest year was 20%. The increase in diffuse radiation was 1.9 kWh/m2 per year, corresponding to 20 years’ growth of up to 7 %. The annual diffuse radiation of nearly 19 % varied from the least cloudy year to the cloudiest year. A small increase was measured for the ambient air temperature. The measurements showed a yearly increase of 0.04 K per year. The average yearly ambient air temperature variation from the coldest to the warmest year was 3.1 K. According to the seasonal growth of the parameters measured, the ambient air temperature and diffuse radiation increased the most in the summer period, while the global radiation significantly increased in the spring months. The calculations of the solar collector's thermal performance in Lyngby showed that the energy output was mostly dependent on beam radiation. The ambient air temperature did not have a high influence on the thermal performance of the solar collectors compared to the influence of the total solar radiation.

scholarly journals Edge Cooling of a Fuel Cell during Aerial Missions by Ambient Air

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1432
Author(s):  
Lev Zakhvatkin ◽  
Alex Schechter ◽  
Eilam Buri ◽  
Idit Avrahami
Keyword(s):  
Fuel Cell ◽  
Numerical Model ◽  
Wind Tunnel ◽  
Boundary Conditions ◽  
Air Temperature ◽  
Numerical Models ◽  
Heat Removal ◽  
Ambient Air ◽  
Experimental Setup ◽  
Good Agreement

During aerial missions of fuel-cell (FC) powered drones, the option of FC edge cooling may improve FC performance and durability. Here we describe an edge cooling approach for fixed-wing FC-powered drones by removing FC heat using the ambient air during flight. A set of experiments in a wind tunnel and numerical simulations were performed to examine the efficiency of FC edge cooling at various flight altitudes and cruise speeds. The experiments were used to validate the numerical model and prove the feasibility of the proposed method. The first simulation duplicated the geometry of the experimental setup and boundary conditions. The calculated temperatures of the stack were in good agreement with those of the experiments (within ±2 °C error). After validation, numerical models of a drone’s fuselage in ambient air with different radiator locations and at different flight speeds (10–30 m/s) and altitudes (up to 5 km) were examined. It was concluded that onboard FC edge cooling by ambient air may be applicable for velocities higher than 10 m/s. Despite the low pressure, density, and Cp of air at high altitudes, heat removal is significantly increased with altitude at all power and velocity conditions due to lower air temperature.

Is It Possible to Obtain More Energy from Solar DH Field? Interpretation of Solar DH System Data

2021 ◽  
Vol 25 (1) ◽  
pp. 1284-1292
Author(s):  
Roberts Kaķis ◽  
Ilze Poļikarpova ◽  
Ieva Pakere ◽  
Dagnija Blumberga
Keyword(s):  
Air Temperature ◽  
Solar Collector ◽  
Large Scale ◽  
District Heating ◽  
Ambient Air ◽  
Energy Sector ◽  
Climatic Conditions ◽  
Water Tank ◽  
System Productivity ◽  
Ambient Air Temperature

Abstract Europe has a course to zero emissions by 2050, with a strong emphasis on energy sector. Due to climatic conditions in Latvia, district heating (DH) plays an important role in the energy sector. One of the solutions to achieve the set goals in DH is to introduce emission-free technology. Therefore, the popularity of installation of large-scale solar collector plants continues to increase in DH in Europe. The first large-scale solar collector field in the Baltic States was installed in 2019. Solar collector active area is 21 672 m2 with heat storage water tank 8000 m3. The article shows the first operation results of this system and evaluates influencing factors. The results of the analysis show that system productivity is mainly demanded by solar radiation, and the strongest correlation between these parameters were established in May. The highest correlation between ambient air temperature and produced thermal energy is reached when ambient air temperature is between 7 °C to 15 °C and production process has not been externally regulated. The temperature difference between flow and return temperatures of the heat carrier affect solar collector performance minimally and strong correlation was not observed.

Flow Visualization and Air Temperature Measurements in Symmetrically Heated Vertical Channels With Adiabatic Extensions

2002 ◽  
Author(s):  
Oronzio Manca ◽  
Marilena Musto ◽  
Vincenzo Naso
Keyword(s):  
Flow Visualization ◽  
Air Temperature ◽  
Process Parameters ◽  
Thermal Performance ◽  
Vertical Channel ◽  
Ambient Air ◽  
Expansion Ratio ◽  
Uniform Heat Flux ◽  
Thermal Plume ◽  
Cold Air

Air natural convection in a vertical channel-chimney system with the channel walls symmetrically heated at a uniform heat flux has been experimentally investigated. Flow visualization photographs and average air temperatures are presented. Some profiles of air temperature fluctuations are reported, which point out the fluid flow interactions in the chinmey. The flow visualization showed that the cold air inflow penetrating into the chimney affects the thermal performance of the channel. The improvement in the thermal performance of the channel determined by the chimney effect, for various values of the process parameters, has also been pointed out. In all investigated configurations and ranges of the process parameters the air flow in the channel was laminar. The flow in the chimney is strongly affected by the aspect ratio. Moreover, at the lower values of the expansion ratio the flow was laminar in the chimney and in its lower corner a stable vortex was noticed whereas at larger values of the expansion ratio a cold ambient air downflow worsened the thermal performance of the system. Interactions between the thermal plume arising from the channel, the vortex in the comer in the inlet chimney region and the cold air inflow yield fluctuations in the air temperature in the system. The distribution of time averaged air temperature in the cross sections validates indications given by the flow visualization in the chimney.

Using a Windbreak to Improve the Thermal Performance of a Flat Plate Solar Collector: A Feasibility Study

2011 ◽  
Author(s):  
Saeed Moaveni ◽  
Michael C. Watts
Keyword(s):  
Flat Plate ◽  
Heat Loss ◽  
Forced Convection ◽  
Thermal Performance ◽  
Solar Collector ◽  
Large Scale ◽  
Ambient Air ◽  
Absorber Plate ◽  
Wide Range ◽  
Flat Plate Solar Collector

During the past few decades, a wide range of studies have been performed to improve the performance of flat plate solar collectors by either reducing the heat loss from a collector or by increasing the amount of solar radiation absorbed by the absorber plate. Examples of these studies include adding transparent honeycomb to fill the air gap between the glazing and absorber plate to reduce convective heat loss, replacing the air in the gap by other gases such as Argon, Krypton, Xenon and Carbon Dioxide, or adding a chemical coating such as Copper Oxide to increase absorbtance and reduce the emittance of the absorber plate. While these methods improve the collector’s efficiency, they focus primarily on limiting the natural convection that occurs in the collector cavity, or on improving the optical properties of the absorber or glazing. None of these studies have addressed the problem of heat loss due to forced convection to the surrounding ambient air in any detail. Yet, research has shown that forced convection will contribute significantly to the heat loss from a collector. Windbreaks have traditionally been used to direct wind to protect farmland, and to direct wind drifts and sand dunes. Windbreaks also have been shown to provide protection for homes from winter winds which result in reduced heating costs for buildings. While windbreaks have been traditionally used for large scale applications, there is reason to believe that similar benefits can be expected for scaled down applications such as adding a windbreak along side of a flat-plate solar collector. In this paper, we examine the feasibility of using a windbreak to provide a flat plate solar collector protection from the wind in order to improve its performance. A series of experiments were performed wherein the thermal performance of two flat-plate collectors — one without a windbreaker and one with a windbreaker — were measured. The results of these experiments are reported in this paper and the need for further studies to explore different windbreak configurations is discussed.

scholarly journals Simulation of Thermal Performance and Cost Benefits of Cool Roof Options through Building Engineering System Software

2020 ◽  
Vol 39 (4) ◽  
pp. 806-814
Author(s):  
Aftab Ahmed Sahito ◽  
Rizwan Ahmed Memon ◽  
Khanji Harijan ◽  
Pervez Hameed Shaikh
Keyword(s):  
Air Temperature ◽  
Thermal Performance ◽  
Temperature Difference ◽  
Energy Savings ◽  
Payback Period ◽  
Engineering System ◽  
Cool Roof ◽  
Cost Benefits ◽  
Save Energy ◽  
Building Engineering

The cool roofs in buildings is a promising option to deal with summer Urban Heat Island (UHI) effects. In context to that, studies on different cool roof materials are widely available; however, there is a dearth of studies on insulating material benefits and implication for tropical and sub-tropical climate zones. This work investigates thermal performance, energy savings and cost benefits of cool roof materials. For this study, simulation of various cool roof materials such as Marble, Expanded Polyurethane Spray (EPS), Poly Vinyl Chloride (PVC), Spray Polyurethane Foam (SPF) , Extruded Polystyrene Foam (XPS), Thermocol sheet, Asphalt tile, Gypsum tile and Jumbolon-board have been carried out using Energy Plus software package. The results of zone air temperature show that maximum zone air temperature occurs in the month of May. The maximum zone air temperature obtained for conventional roof is 32.1oC, whereas that for Thermocol sheet, SPF, XPS, Jumbolon-board, EPS, marble, PVC, Asphalt tile and Gypsum tile is 28.8, 28.9, 28.8, 29, 29.1, 31.9, 30.5, 30.2 and 30.7oC respectively. Conventional roof surface outside and inside temperature difference is 2.90C, whereas, roof surface outside and inside temperature difference for Thermocol sheet, XPS, Jumbolon-board, SPF, EPS, marble, PVC, asphalt tile and gypsum tile is 9.2, 9.3, 8.7, 7.5, 8.1, 3, 3.1, 3.3 and 2.20C, respectively. Notably, XPS, Thermocol sheet, SPF, Jumbolon-board, EPS, Marble, PVC, Asphalt tile and Gypsum tile cool roof materials can save around 5.47, 5.38, 5.35, 5.15, 4.93, 1.09, 2.62, 2.31 and 2.18 MWh annually, respectively for the selected building. The payback period for marble, PVC, gypsum tile and asphalt tile is above 1 year, whereas the effective payback period obtained for XPS, Thermocol sheet, SPF, EPS and Jumbolon-board varies from 3 to 6 months. It is concluded that the cool roof materials may be used effectively to save energy and cost.

scholarly journals Numerical Simulation Investigation of a Double Skin Transpired Solar Air Collector

2022 ◽  
Vol 12 (1) ◽  
pp. 520
Author(s):  
Charles Berville ◽  
Florin Bode ◽  
Cristiana Croitoru
Keyword(s):  
Numerical Simulation ◽  
Solar Collector ◽  
Ambient Air ◽  
Point Of View ◽  
Airflow Rate ◽  
Solar Collectors ◽  
A Value ◽  
Double Skin ◽  
Separation Plate ◽  
Guide Values

Transpired solar collectors (TSC) are one of the most popular solar thermal technologies for building façades. TSC use solar energy to heat the absorber surface, which transmits thermal energy to the ambient air. A variant of TSC, namely, a double skin transpired solar collector (DSTSC), has been analyzed in this paper, thus providing guide values and a technical point of view for engineers, architects, and constructors when designing such transpired solar collectors. Three important parameters were addressed in this study through numerical simulation: the influence of a separation plate introduced in a TSC, turning it into a DSTSC; the air layer thickness influence on the performance of the collector; and the influence of the used absorber materials for the separation plate material. Greater heat exchange efficiency was noticed for the DSTSC at every imposed airflow rate compared with the TSC. Regarding the thickness of the collector, the efficiency gradually increased when increasing the solar collector thickness until it reached a value of 20 cm, though not varying significantly at a thickness of 30 cm.

scholarly journals An Experimental Study on Double-Glazed Flat Plate Solar Water Heating System in Turkey

2014 ◽  
Vol 564 ◽  
pp. 204-209 ◽  
Author(s):  
Ahmet Ozsoy ◽  
Sabahattin Demirer ◽  
Nor Maria Adam
Keyword(s):  
Experimental Study ◽  
Flat Plate ◽  
Air Temperature ◽  
Temperature Difference ◽  
Solar Collector ◽  
Heating System ◽  
Ambient Air ◽  
Hot Water ◽  
Solar Simulator ◽  
Ambient Air Temperature

Domestic hot water preparation systems with flat plate solar collectors are widely used in Turkey. In this collector, the temperature difference between the required water temperature and the ambient air temperature increase causes a decrease in the efficiency of the collector. In this study, the use of double glass in order to increase the efficiency of the collector is studied experimentally.The location is in Isparta South West Turkey. Experimental study is conducted in May 2013 at the Suleyman Demirel University, Isparta. The system components are solar simulator, solar collector, tank, circulation pump, flowmeter, thermocouples, data acquisition device and solar sensor. Solar collector system’s operating temperature is 50oC for winter also summer. The difference between the collector temperature and the ambient air temperature exceeds 25oC in many cases, were found to be more efficient double-glazed collectors. When the temperature difference is 40oC, using double glazing collector is 24% more efficient than using single glazing collector.

scholarly journals Field Experiments to Evaluate Thermal Performance of Energy Slabs with Different Installation Conditions

2018 ◽  
Vol 8 (11) ◽  
pp. 2214 ◽  
Author(s):  
Seokjae Lee ◽  
Sangwoo Park ◽  
Minkyu Kang ◽  
Hangseok Choi
Keyword(s):  
Heat Exchange ◽  
Thermal Insulation ◽  
Air Temperature ◽  
Thermal Performance ◽  
Field Experiments ◽  
Side Wall ◽  
Ambient Air ◽  
Test Bed ◽  
Interior Space ◽  
Ambient Air Temperature

The energy slab is a novel type of horizontal Ground Heat Exchanger (GHEX), where heat exchange pipes are encased in building slab structures. The thermal performance of energy slabs is usually inferior to the conventional closed-loop vertical GHEX because its installation depth is relatively shallow and therefore affected by ambient air temperature. In this paper, heat exchange pipes were made of not only conventional high-density polyethylene (HDPE), but also stainless steel (STS), which is expected to enhance the thermal performance of the energy slabs. In addition to a floor slab, a side wall slab was also used as a component of energy slabs to maximize the use of geothermal energy that can be generated from the underground space. Moreover, a thermal insulation layer in the energy slabs was considered in order to reduce thermal interference induced by ambient air temperature. Consequently, two different field-scale energy slabs (i.e., floor-type and wall-type energy slabs) were constructed in a test bed, and two types of heat exchange pipes (i.e., STS pipe and HDPE pipes) were installed in each energy slab. A series of thermal response tests (TRTs) and thermal performance tests (TPTs) were conducted to evaluate the heat exchange performance of the constructed energy slabs. Use of the STS heat exchange pipe enhanced the thermal performance of energy slabs. Additionally, the wall-type energy slab had a similar thermal performance to the floor-type energy slab, which infers the applicability of the additional use of the wall-type energy slab. Note that if an energy slab is not thermally cut off from the building’s interior space with the aid of thermal insulation layers, heat exchange within the energy slabs should be significantly influenced by fluctuations in ambient temperature.

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