Thermal Load Calculation Research Articles

ANALYSIS OF THERMAL LOAD CALCULATIONS IN STEEL SILOS: A COMPARISON OF EUROCODE 1, CLASSICAL METHODS, AND FINITE ELEMENT METHODS

Thermal loads can result in significant increases in grain pressure in silos. Eurocode 1 part 4 recognizes this action, but does not propose a calculation method for its measurement. The purpose of this study is to analyze and compare classical models for thermal load calculation with finite element models developed by the authors.

A-4 最大熱負荷計算用の屋外温湿度条件の見直し(その2) : 関東地区における設計用外気条件と最大熱負荷の地域差に関する検討

A-4 最大熱負荷計算用の屋外温湿度条件の見直し(その2) : 関東地区における設計用外気条件と最大熱負荷の地域差に関する検討

A-3 最大熱負荷計算用の屋外温湿度条件の見直し : その1 見直しの概要と全国の設計外気条件に関する検討

A-3 最大熱負荷計算用の屋外温湿度条件の見直し : その1 見直しの概要と全国の設計外気条件に関する検討

Análisis de cálculo de las cargas térmicas en silos metálicos mediante el Eurocódigo 1, los métodos clásicos y el método de los elementos finitos

Thermal loads cause important increases in the pressures exerted by granular material stored in silos. The Eurocode 1, part 4, establishes their importance, but it does not propose any calculation method that allows their quantification. In this work the authors try to overcome this difficulty analyzing and comparing different classic methods of calculation of thermal loads and models developed by the authors using the Finite Element Method.

A novel and simple building load calculation model for building and system dynamic simulation

Based on polynomial s-transfer functions of transient heat conduction through a building construction, a novel and simple model is developed for building thermal load calculation. The polynomial s-transfer functions are estimated from the theoretical frequency responses of the building construction by frequency-domain regression method. The simple polynomial s-transfer functions are completely equivalent to the hyperbolic s-transfer functions in terms of frequency characteristics. First, the frequency responses of the total transmission matrix are calculated within the frequency range concerned. Then, a set of linear equations is solved yielding a simple polynomial s-transfer function for cross and internal heat conduction. Finally, simple recursive formulae are obtained by inverse Laplace transforms and discretization of the convolution integrals. The coefficients of the model are independent from time step and the time step can be varied according to the requirement during simulation. Validations and comparisons show that this model has fast computation speed and no numerical unstability, and provides high accuracy and good flexibility to the requirement of variable time step.

Mixed convection from heated room surfaces

In most building thermal load calculations natural convective heat transfer is assumed for internal room surfaces. When mechanical ventilation is used, the natural convective heat transfer coefficient (CHTC) will underestimate the convective heat transfer from the room surface. In this paper, measured local and surface-mean convective heat transfer data are presented for convection from a heated surface partially covered by an air jet. Experiments were conducted in a small office-sized, well-insulated environmental chamber with heating plates fixed to the internal surfaces. A fan box with an adjustable nozzle was placed at one end of the surfaces within the chamber to create the convective flow. Cooling was provided at one wall to represent a heat sink. Equations are presented for predicting mixed convection heat transfer as a combination of natural and forced convection for walls, floor and ceiling. When the jet acted on a heated surface the measured CHTC was greater than the equivalent natural convection CHTC, although the increase for the ceiling was much greater than for the floor or wall.

Technology, thermal analysis and economic evaluation of a sunspace located in northern Greece

This paper discusses the thermal analysis and economic performance of an attached sunspace, used in a conventional dwelling environment. The sunspace is a modified greenhouse with special geometry of glazed inclined roof and inclined glazed walls and is capable to operate only as a completely passive system. New solar radiation and ambient temperature data for the area of northern Greece is presented. The calculation of thermal loads using the degree–day method and the annual auxiliary energy requirements of the residence are estimated using the unutilizability method (UU method). The economic analysis is performed using the Life Cycle Savings (LCS) method, modified to comply with the Greek tax policy, and the cost-optimum collector's area determination using the P-chart method. Also, the payback period of the initial investment is estimated, after taking under consideration economic factors applied to Greek energy policy.

Thermal Load Calculations at TJ-II Vacuum Vessel under Neutral Beam Injection

The neutral beam power transmitted into the helical axis stellarator TJ-II is calculated for the final duct design of TJ-II. The transmitted beam is intercepted by the first toroidal field coil before reaching the plasma. The nontrapped fraction of the beam hits various vacuum vessel components.The adopted design of the graphite thermal shields used as vacuum vessel protection at TJ-II is presented. The design achieves a compromise between maximum power into the torus and minimum loads on sensitive parts.A three-dimensional version of the beam geometric code DENSB is set up to calculate the power loads due to shine-through neutrals on the shields under these circumstances. Power load maps are the input to the finite element code ANSYS for the calculation of temperature distributions.For the usual duty cycle at TJ-II (300-ms pulses every 300 s), the peak surface saturation temperatures at all surfaces remain under 650 °C, well below the tolerable limits for graphite.

Calculation of Critical Thermal Loads under Extreme Intensities of Mass Forces

Calculation of Critical Thermal Loads under Extreme Intensities of Mass Forces

Test results of a 1 kA (2 kA)-20 kV HTSC current lead model

Within the framework of the European BRITE/EURAM project, a d.c. 1 kA (2kA)-20 kV hybrid superconducting current lead pair has been designed, built and tested. It is composed of copper conductors for the electrical connection from room temperature to an intermediate temperature T int (77 K) and high T c superconducting tubes conducting the current down to liquid helium temperature. The high T c parts are cooled by solid state heat conduction towards a helium bath and the copper parts make use of cold nitrogen vapour which is produced during operation of the lead. Bi 2Sr 2CaCu 2O 8+δ melt-cast processed tubes, 200 mm long, are placed in an insulating vacuum and are connected to the two thermal reservoirs by suitable copper connections. Test results for currents up to twice the nominal value (i.e. 2000 A) are given. Thermal and electrical measurements are presented, showing that the overall refrigeration load, comprising the metallic 300 K- T int part and the superconducting 4.2 K- T int part, are reduced by a factor of five with respect to vapour cooled, all-metal current leads. These results are compared to thermal load calculations of high temperature current leads.

Selection of an “example weather year” for Hong Kong

An example weather year has been established for Hong Kong to facilitate thermal load and energy demand calculation for buildings. The selection process involved the studying of meteorological data for the years 1967–1991 and eliminating the years which contain any monthly mean of weather parameter that differs significantly from the long-term mean of the particular month. It is recommended that the calendar year 1989 be selected as the example weather year for Hong Kong. A summary of the meteorological data for the proposed example year is also included for reference and the energy demand calculation.

EFFECT OF CYCLIC THERMAL LOADING ON THE PROPERTIES OF METAL MATRIX COMPOSITES

The properties of metal matrix composites subjected to mechanical and cyclic loading are investigated. It is demonstrated that the methods of Gokhfeld and Ponter that have been developed to determine the elasticfplastic response of mechanical structures can be extended to establish the effect of thermal loading on the behavior of metal matrix composites. The procedure makes use of the elastic solution for thermal cycle loading and limit load calculations.

Temperature and humidity control system in a lunar base

An increasing number of lunar base construction programs are in the process of developing lunar resources such as helium 3. The objective of the present work is to evaluate the temperature and humidity control system, which will allow man to live and work on the moon while developing lunar resources. The results of thermal load calculation show that the load of electric lighting is a 80 to 90% of the cooling load in the habitat module and that only the cooling function is required for temperature control. Due to this, a fluorocarbon refrigerant heat pump system was selected to satisfy reliability, energy consumption, size and weight requirements for the lunar base equipment. According to the load calculation, occupants will feel discomfort due to radiant heat from lighting fixtures. To resolve this problem, an air conditioning system, used in combination with forced convective cooling and panel cooling on the ceiling, was adopted in the living space. Moreover, the experiment on the ground was carried out to evaluate the effects of panel cooling.

Evaluation and control of thermal gains through Iraqi windows

Abstract A simple procedure, based on solar profile angles, is presented for the selection of appropriate overhangs for south facing windows in Iraq. Using local weather data the results of a heat transmission analysis due to solar radiation as well as temperature difference across glazed areas are given. Summer and winter performance of appropriate horizontal and vertical projections in controlling hourly heat transmission through windows at various orientations are presented. The results aid designers in window and overhang selection and air-conditioning engineers in estimating the contribution of fenestration in building thermal load calculations.

Effects of Radiant Heat upon the Thermal Load of a Heated Room : Part 2-A Statistical Analysis of Results of Numerical Experiments about the Heat Loss from a Heated Room as well as Introduction of a New Simplified Method for Calculation of Room Thermal Load

Effects of Radiant Heat upon the Thermal Load of a Heated Room : Part 2-A Statistical Analysis of Results of Numerical Experiments about the Heat Loss from a Heated Room as well as Introduction of a New Simplified Method for Calculation of Room Thermal Load

Periodic heat flux through extended structures and projections of buildings

An explicit expression for periodic heat flux through extended structures and projections has been obtained in terms of Fourier series. Numerical results show that it is imperative to include hourly variation of solair and ambient temperatures for realistic thermal load calculation of buildings with projections. It is interesting to note that projections may enhance or reduce thermal fluctuations in the incoming heat flux depending upon their transverse dimensions.

Building analysis system — BAS

In our laboratory we use several different programs dealing with the same fundamental problem: the calculation of thermal loads and annual consumptions. The programs must by used at different stages of the design process. The main disadvantage of using separate programs can disappear if the programs are gathered in a single structure with one entry point.

空調熱負荷算法における時系列重み係数の決定に関する研究

This paper discusses the general techniques of calculating weighting factors in time series method in the unsteady state heat flow in the air conditioning thermal load calculations. It is shown first that the weighting factors WX_j relating space cooling load to heat gain of surface heat flow, can be obtained by solving simultaceous equations, taking account of radiation exchange among the surfaces of enclosed space including the effect of radiation absorption and emmission by water vapor in the space. Then the thermal characteristics of WX_j factors and the calculation techniques of weighting factors relating space cooling load to various heat gains using WX_j factors are described. Finally it is pointed out that the space heat extraction is to be affected remarkably by WX_j, particularly in the case of intermittent operation of air conditioning.