Evaluation of the Cover Glasses in Solar Cookers Box-Type Considering Conduction Heat Losses in Four Different Solar Cookers

2016 ◽  
Author(s):  
Hilario Terres ◽  
Sandra Chavez ◽  
Raymundo Lopez ◽  
Arturo Lizardi ◽  
Araceli Lara
Keyword(s):  
Solar Radiation ◽  
Heat Loss ◽  
Experimental Tests ◽  
Heat Losses ◽  
Cooking Time ◽  
Heating Process ◽  
Labview Software ◽  
Radiation Losses ◽  
Compact Field

A evaluation of the conduction heat loss over their cover for four different solar cookers box-type (1. Square solar cooker with inner reflectors placed in right angles, 2. Square solar cooker with inner reflector placed in different angles, 3. Rectangular solar cooker with inner reflectors placed in different angles and 4. Octagonal solar cooker with inner reflectors placed in right angles) is presented. In the heating process in a solar cooker box-type, the conduction heat loss in their cover is the most important in comparative with convection and radiation losses. The cover in solar cookers is made with clear glasses, which allows the inlet solar radiation inside of it. When the heating process happen, the temperature in the cover glasses is important and is important for this part. To evaluate the magnitude for the heat loss, controlled tests were planned, where a solar radiation simulator was used as energy source over the solar cookers considered. In the experiments, thermocouples to determine the gradient temperature for thickness among glasses were placed. In this activity, a Compact Field and LabView software were used. Also, in the experimental tests, thermographic imagines for some instants during the heating process were taken. According results, the conduction heat losses are bigger than 25 % of the inlet energy Flux in the cookers. The biggest values for temperature on the glasses correspond to the solar cooker 3, while minimum values are obtained for the solar cooker 1. The solar cooker 1 present the biggest conduction heat losses and the cooker 4, has the minimum values for the losses. Results of this work can be useful and important for design proposes which could impacts on save of money and cooking time.

COMPUTER MODELING OF THE STRUCTURE OF FOREST DRYING CHAMBERS, REDUCING HEAT LOSS

2020 ◽  
Vol 2020 (4) ◽  
pp. 60-67
Author(s):  
Boris Pruss ◽  
Viktor Romanov ◽  
Yaroslav Prozorov ◽  
Olga Pleskacheva
Keyword(s):  
Computer Modeling ◽  
Heat Loss ◽  
Heat Losses ◽  
Heat Energy ◽  
Insulating Materials ◽  
Sawn Timber ◽  
Drying Chamber

The paper presents the theory of calculating heat loss through the fences of timber drying chambers. The software for computer modeling of the process of transferring heat energy through the fences of the drying chamber, consisting of various heat-insulating materials, for calculating heat losses during drying of sawn timber is described. The efficiency of the use of modern heat-insulating materials to reduce heat losses during drying of sawn timber has been experimentally confirmed.

DYNAMICS OF THERMAL LOSSES BY CONVECTION AND RADIATION OF THE SPHERICAL HEAT ACCUMULATOR OF SOLAR PLANTS

2020 ◽  
Vol 4 (41) ◽  
pp. 57-62
Author(s):  
SHAVKAT KLYCHEV ◽  
◽  
BAKHRAMOV SAGDULLA ◽  
VALERIY KHARCHENKO ◽  
VLADIMIR PANCHENKO ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Heat Loss ◽  
Initial Conditions ◽  
Water System ◽  
Heat Losses ◽  
Research Purpose ◽  
Heat Accumulator ◽  
Water Heaters ◽  
Intrinsic Radiation ◽  
Over Time

There are needed energy (heat) accumulators to increase the efficiency of solar installations, including solar collectors (water heaters, air heaters, dryers). One of the tasks of designing heat accumulators is to ensure its minimal heat loss. The article considers the problem of determining the distribution of temperatures and heat losses by convection and radiation of the heat insulation-accumulating body (water) system for a ball heat accumulator under symmetric boundary conditions. The problem is solved numerically according to the program developed on the basis of the proposed «gap method». (Research purpose) The research purpose is in determining heat losses by convection and radiation of a two-layer ball heat accumulator with symmetric boundary conditions. (Materials and methods) Authors used the Fourier heat equation for spherical bodies. The article presents the determined boundary and initial conditions for bodies and their surfaces. (Results and discussion) The thickness of the insulation and the volume of the heat accumulator affect the dynamics and values of heat loss. The effect of increasing the thickness of the thermal insulation decreases with increasing its thickness, starting with a certain volume of the heat accumulator or with R > 0.3 meters, the heat losses change almost linearly over time. The dynamics of heat loss decreases with increasing shelf life, but the losses remain large. (Conclusions) Authors have developed a method and program for numerical calculation of heat loss and temperature over time in a spherical two-layer heat accumulator with symmetric boundary conditions, taking into account both falling and intrinsic radiation. The proposed method allows to unify the boundary conditions between contacting bodies.

scholarly journals Solar Radiation and Vitamin D: Mitigating Environmental Factors in Autoimmune Disease

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Gerry K. Schwalfenberg
Keyword(s):  
Rheumatoid Arthritis ◽  
Multiple Sclerosis ◽  
Inflammatory Bowel Disease ◽  
Vitamin D ◽  
Type 1 Diabetes ◽  
Autoimmune Disease ◽  
Solar Radiation ◽  
Inflammatory Bowel

This paper looks at the environmental role of vitamin D and solar radiation as risk reduction factors in autoimmune disease. Five diseases are considered: multiple sclerosis, type 1 diabetes, rheumatoid arthritis, autoimmune disease of the thyroid, and inflammatory bowel disease. Clinical relevant studies and factors that may indicate evidence that autoimmune disease is a vitamin D-sensitive disease are presented. Studies that have resulted in prevention or amelioration of some autoimmune disease are discussed. An example of the utility of supplementing vitamin D in an unusual autoimmune disease, idiopathic thrombocytic purpura, is presented.

scholarly journals Reduction of Heat Losses in a Pre-Insulated Network Located in Central Poland by Lowering the Operating Temperature of the Water and the Use of Egg-shaped Thermal Insulation: A Case Study

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2104 ◽  
Author(s):  
Dorota Anna Krawczyk ◽  
Tomasz Janusz Teleszewski
Keyword(s):  
Heat Loss ◽  
Thermal Insulation ◽  
Heat Losses ◽  
Ecological Effect ◽  
Operation Temperature ◽  
Supply Pipe ◽  
Insulation Thickness ◽  
Network Operation ◽  
Cross Section Geometry

This paper presents possible variants of reducing the heat loss in an existing heating network made from single pre-insulated pipes located in central Europe. In order to achieve this aim, simulations were carried out for five different variants related to the modification of the network operation temperature, replacement of a single network with a double pre-insulated one, and changes in the cross-section geometry of the thermal insulation of the double heating network from circular to egg-shaped. The proposed egg-shaped thermal insulation was obtained by modifying the shape of the Cassini oval, in that the supply pipe has a greater insulation thickness compared to the return pipe. The larger insulation field in the supply pipe contributed to reducing the heat flux density around the supply line and, as a result, to significantly reducing heat loss. The egg-shaped thermal insulation described in the publication in a mathematical formula can be used in practice. This work compares the heat losses for the presented variants and determines the ecological effect. Heat losses were determined using the boundary element method (BEM), using a proprietary computer program written as part of the VIPSKILLS 2016-1-PL01-KA203-026152 project Erasmus+.

scholarly journals INSTALLATION FOR DETERMINATION OF HEAT RELEASE OF HEATING RADIATORS

2021 ◽  
Vol 4 (164) ◽  
pp. 77-81
Author(s):  
Yu. Ivashina ◽  
V. Zavodyannyi
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Electrical Power ◽  
Electric Heating ◽  
Middle Part ◽  
Heat Losses ◽  
The Body ◽  
Heat Output ◽  
Stationary Mode

To calculate the share of thermal energy consumed by this apartment in an apartment building, it is necessary to determine the heat transfer of all heating radiators in the house. But the heat transfer given in the passport of the heating device corresponds to the temperature pressure equal to 70K. Often the owners install non-standard devices, so the problem of determining the heat transfer of heating radiators in real conditions is relevant. Thermometric method, which is called electric, is widely used for laboratory determination of heat transfer of heating devices. Water by means of the pump circulates through an electric copper and the investigated radiator. The heat output of the latter is defined as the difference between the supplied electrical power (boiler power plus pump) and heat loss. The purpose of the work is to develop and study the operation of the installation for determining the heat transfer of heating radiators, which had a simpler design and could ensure proper measurement accuracy. We have proposed a scheme and design of the installation for determining the heat transfer of electric heating radiators, which differs in that it does not include a circulating pump. Water in the system circulates under the action of gravity due to changes in the density of the coolant during heating and cooling. This greatly simplifies the circuit by eliminating not only the pump but also the valve and the air outlet valve. The heater chamber is made of a steel pipe with a diameter of 88 mm. A steel cover is attached to the lower flange, through which a 1-1.5 kW heater is introduced into the chamber. Two 1/2 ″ sections of pipe are welded to the body of the heater chamber, through which the radiator is connected by means of rubber couplings. The cylindrical surface of the chamber on top of the layer of internal insulation is covered with a shielding heater, the temperature of which is maintained equal to the surface temperature of the heater chamber in the middle part. A layer of external thermal insulation is installed on top of the shielding heater. To determine heat loss, the radiator is disconnected from the heater chamber, plugs are installed and insulated. In stationary mode, the dependence of the heater power on the temperature of the heater chamber is measured, which determines the power of heat losses. The simplification of the installation has led not only to its reduction in price, but also to an increase in accuracy due to the reduction of heat losses and the simplicity of their definition.

scholarly journals Calculation Of Heat Loss Through The Pipes Of The Interior Central Heating System

2015 ◽  
Vol 5 (2) ◽  
pp. 29-36 ◽  
Author(s):  
I. Giurca
Keyword(s):  
Heat Loss ◽  
Heating System ◽  
Building Energy ◽  
Local Heat ◽  
Heat Losses ◽  
Energy Audit ◽  
Heating Systems ◽  
Central Heating ◽  
Calculation Methodology

Abstract The article presents aspects related to the calculation of heat loss through the pipes of the interior central heating system. The purpose of the article is to detail the local heat losses in case of central heating systems. Based on the conclusions of the article, we propose the modification of the calculation methodology related to the building energy audit.

Heat Loss Analysis of Flamelets in Near-Limit Spread Over Solid Fuel Surfaces

2001 ◽  
Author(s):  
Robert Vance ◽  
Indrek S. Wichman
Keyword(s):  
Heat Loss ◽  
Solid Fuel ◽  
Flame Spread ◽  
Environmental Conditions ◽  
Flame Length ◽  
Heat Losses ◽  
Loss Analysis ◽  
Parabolic Shape ◽  
Flame Sheet ◽  
Surface Decomposition

Abstract The profile of a spreading flamelet is analyzed by examining the heat losses to surrounding surfaces. The study addresses the reasons why flamelets have shapes ranging from round hemispherical “caps” to flat “coin-like” discs. A parabolic shape profile is used for the thin flame sheet, which provides both flame length and flame curvature. A third parameter specifies the height of the flame from the surface beneath it. Radiation and conduction heat losses from the flame sheet are calculated for various flame shapes. Overall heat losses as well as heat losses to the surface beneath the flamelet are examined. Some of the heat “losses” are misnamed because they produce the necessary surface decomposition for subsequent gaseous flame fuel vapors. Strictly, then, “losses” do not contribute appreciably to the maintenance of the flame. Physical arguments are made to explain observed flame spread behavior and flame shapes in response to prevailing flow and environmental conditions.

scholarly journals Impaired whole-body heat loss in type 1 diabetes during exercise in the heat: a cause for concern?

Diabetologia ◽  
2019 ◽  
Vol 62 (6) ◽  
pp. 1087-1089 ◽  
Author(s):  
Sean R. Notley ◽  
Martin P. Poirier ◽  
Jane E. Yardley ◽  
Ronald J. Sigal ◽  
Glen P. Kenny
Keyword(s):  
Type 1 Diabetes ◽  
Heat Loss ◽  
Whole Body ◽  
Body Heat

scholarly journals The influence of heat loss from pipes in an unheated basement on the heating energy consumption of an entire typical apartment building

2020 ◽  
Vol 172 ◽  
pp. 12005
Author(s):  
Anti Hamburg ◽  
Targo Kalamees
Keyword(s):  
Energy Balance ◽  
Heat Loss ◽  
District Heating ◽  
Building Energy ◽  
Energy Performance ◽  
Heat Losses ◽  
Hot Water ◽  
Limited Information ◽  
Apartment Building ◽  
Heating Energy Consumption

The majority of old apartment buildings were designed with an unheated basement. Building service systems such as district heating heat exchangers and pipes for domestic hot water and for space heating are usually located in this unheated basement. In addition, these locations are connected with shafts. All these pipe’s heat losses increase air temperature in the basement. If these losses are included into the building energy balance, then they decrease heat loss through the basement ceiling. The basement’s heat balance is also dependent on heat loss from the basement envelope and outdoor air exchange in the basement. In early stages of design, designers and energy auditors need rough models to make decisions in limited information conditions. Once the effects of heat losses from pipes become apparent, they need to be factored into the buildings energy balance, and their effects on heat loss through the basement ceiling needs to be calculated. In this paper we analyse the effect these heat losses have on the service system’s heat gains and heat loss through an uninsulated basement ceiling at different basement insulation levels and with different thicknesses of pipe insulation. From our study we found that pipe losses in the basement increase the building energy performance value by at least 4 kWh/(m²∙a) and their impact on a renovated apartment building is very important.

Heat and Moisture Transport Through the Micro-Climate Air Annulus of the Clothing-Skin System Under Periodic Motion

2005 ◽  
Author(s):  
N. Ghaddar ◽  
K. Ghali ◽  
E. Jaroudi
Keyword(s):  
Heat Loss ◽  
Latent Heat ◽  
Moisture Transport ◽  
Contact Region ◽  
Heat Losses ◽  
Sensible Heat ◽  
Skin Contact ◽  
Cylinder Model ◽  
Heat And Moisture Transport ◽  
Heat And Moisture

A dynamic thermal model is developed using the 2D cylinder model of Ghaddar et al [1] of ventilated fabric-skin system where a microclimate air annulus separates an outer cylindrical fabric boundary and an inner human body solid boundary for closed and open apertures. The cylinder model solves for the radial, and angular flow rates in the microclimate air annulus domain where the inner cylinder is oscillating within an outer fixed cylinder of porous fabric boundary. The 2-D cylinder model is further developed in the radial and angular directions to incorporate the heat and moisture transport from the inner cylinder when the fabric touches the skin boundary at repetitive finite intervals during the motion cycle. The touch model is based on a lumped fabric transient approach based on the fabric dry and evaporative resistances at the localized touch regions at the top and bottom of points of the cylinder. The film coefficients at the inner cylinder are needed for the model simulation. Experiments are conducted in an environmental chamber under controlled conditions to measure the mass transfer coefficient at the skin to the air annulus separating the wet skin and the fabric in the cylindrical geometry. In addition, experiments have also been conducted at ventilation frequencies of 30, 40, and 60 rpm to measure the sensible heat loss from the inner cylinder to validate the predictions of sensible and latent heat losses of the 2-D ventilation model for the two cases when fabric is in contact with the skin surface and when no contact is present for close aperture. The model prediction of time-averaged steady-periodic sensible heat loss agreed well with the experimentally measured values. A parametric study is performed to predict sensible and latent heat losses from the system by ventilation at different frequencies, fabric skin contact times during the motion cycle measured by a dimensionless amplitude parameter (ζ = amplitude/mean annular spacing). The rate of heat loss increases with increased ventilation frequency at fixed ζ. The latent heat loss in the contact region increases by almost 40% due to increase in fabric temperature during contact. The sensible heat loss decreases between 3% at f = 60 rpm, and 5% at f = 25 rpm in the contact region due to higher air temperature and lack of heat loss by radiation during the contact between fabric and skin.

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