Heat Balance Model Research Articles

Analysis on Steady-State Operation and Heat Loss of Chinese Integrated Pressurized Water Reactor

Chinese integrated pressurized water reactor (CIPWR) has compact configuration and high inherent safety, which is appropriate for nuclear power plants of small and medium scale. Heat balance model has been adopted widely in thermal power calibration of PWRs because of its advantage of accuracy. In this paper, a package based on FORTRAN language is developed and added into RELAP5 to calculate the heat loss value needed in heat balance analysis. The steady-state operation of CIPWR is modelled correctly by RELAP5. The heat loss of CIPWR is calculated by the package, and the comparison of the main values of parameters needed in the heat loss calculation between RELAP5 and the package has been done. It shows that the package has high calculation accuracy and can be applied in reactor design and monitoring.

Preliminary Development of Thermal Power Calculation Code H-Power for a Supercritical Water Reactor

SCWR (Supercritical Water Reactor) is one of the promising Generation IV nuclear systems, which has higher thermal power efficiency than current pressurized water reactor. It is necessary to perform the thermal equilibrium and thermal power calculation for the conceptual design and further monitoring and calibration of the SCWR. One visual software named H-Power was developed to calculate thermal power and its uncertainty of SCWR, in which the advanced IAPWS-IF97 industrial formulation was used to calculate the thermodynamic properties of water and steam. The ISO-5167-4: 2003 standard was incorporated in the code as the basis of orifice plate to compute the flow rate. New heat balance model and uncertainty estimate have also been included in the code. In order to validate H-Power, an assessment was carried out by using data published by US and Qinshan Phase II. The results showed that H-Power was able to estimate the thermal power of SCWR.

Performance of Direct Evaporative Cooling System under Egyptian Conditions

The main objective of this research is to optimize the parameters affecting the performance of the direct evaporative cooling system, to achieve that, a mathematical model of heat and mass balance of the evaporative cooling pads was developed to predict most important factors affecting the performance of the system. The model was able to predict the temperature, humidity ratio, wet bulb effectiveness, dew point effectiveness and temperaturehumidity index of outlet air at different ambient air temperatures (25, 30, 35 and 40°C), different inlet air velocities (1.5, 3, 4.5 and 6 m s-1), ambient air humidities (0.01, 0.02, 0.03 and 0.04 kg kg-1) and different lengths of pad (0.5, 1.0, 1.5 and 2.0 m). The results showed that the outlet temperature increases with increasing ambient temperature, inlet air velocity, ambient air humidities and lengths of pad. The results also showed that the wet bulb effectiveness ranged from 0.927 to 1.086. The dew point effectiveness ranged from 0.561 to 0.747. The humidity ratio ranged from 0.027 to 0.035 kg kg-1. The temperature-humidity index ranged from 21.15 to 33.56°C on study treatments. The predicted outlet temperatures were in a reasonable agreement with those measured, where, it ranged 17.027 to 29.978°C theoretically while it was from 19.605 to 30.748°C experimentally. The prediction of temperature determines the optimum condition of plant growth in greenhouse, so that the model helps this optimization.

Heat and Mass Balance for Baking Process

The main objective of this research was to develop a mathematical model of heat and mass balance of the bread baking process to predict the temperature and water content of bread at different heating temperatures and times. The model was able to predict the bread temperature and water content at different oven temperatures (180, 190, 200, 210 and 220°C). The results showed that the bread temperature and weight loss of bread increase with increasing oven temperature, when, the oven temperature increased from 180 to 220°C, the temperature of bread increased from 112.73 to 168.49°C and the weight loss of bread increased from 22.40 to 52.46%. The results also showed that the bread temperature and weight loss of bread increase with increasing time, this increment starts to decline after 18-20 min, until it reach equilibrium after 30 min. The weight loss of bread increases with increasing bread temperature. It indicates that when the bread temperature increased from 20.00 to 131.69°C, the weight loss of bread increased from 0.00 to 40.79% at 200°C oven temperature. The model was validated with an experimental data and showed a reasonable agreement with those measured, where; it ranged 20.00 to 131.69°C theoretically while it was from 25.00 to 119.00°C experimentally during the baking at 200°C oven temperature. The weight loss data was in a reasonable agreement with those measured, where; it ranged 0.00 to 40.79% theoretically while it was from 0.00 to 48.69% experimentally during the baking at 200°C oven temperature.

A Simplified Method for Estimating Outflow from the Bottom of Snowpack

To ensure the safety of train operations, it is important to estimate the outflow from the bottom of snowpack which might incur a full-depth avalanche. Therefore, the authors examined a simplified method for estimating the outflow from the bottom of snowpack, which can be applied to railway disaster prevention, on the basis of heat balance observations, snowmelt observations and previous studies. Consequently, the simplified method, which combines a snowmelt (heat balance) model and a percolation model, yields a good estimate of the outflow from the bottom of snowpack at 1 hour intervals using four input data available from the nearest AMeDAS: i.e., air temperature, precipitation, wind speed and duration of sunshine.

Overall Assessment of Indoor Conditions in a School Building: an Italian Case Study

Current standards for indoor comfort are based on studies of adults, but they also apply tochildren, even though children differ in terms of metabolic rates, clothing types, activity levels, and preferences in space arrangement. Children are also more sensitive to a range of environmental factors, they are usually unable to interact with their environment, and they accept indoor conditions passively. This study aims to extend research into indoor environmental quality (IEQ) for children by providing analysis, measurements and surveys carried out in an Italian primary school. Continuous monitoring was combined with a detailed spot monitoring campaign, during which pupils completed a questionnaire so that subjective and objective evaluations could be compared. Thermal comfort was also evaluated by comparing pupils’ sensations based on the two most common approaches: the heat balance and adaptive comfort models. Tests revealed that there was no clear, uniform correspondence between subjective response and acoustic and thermal measurements. Children reacted actively to discomfort, suggesting that they should be allowed to interact with their environment. Building acoustics were also measured in order to evaluate the insulating properties of building elements. The following tests were conducted: facade sound insulation, sound insulation of the vertical and horizontal partitions between classrooms, and the impact levels between overlapped classrooms. Reverberation time and background noise were measured in unoccupied, furnished classrooms after school hours. Impulse response and Speech Transmission Index (STI) measurements were also performed in one classroom.

Mathematical Model of Compost Pile Temperature Prediction

A mathematical model of heat balance was developed to predict the compost temperature during the maturation stage. The components of the energy balance of the compost pile which include: heat gained (heat generation and solar radiation) and heat lost (radiation, evaporation, convection, and conduction) at different ambient temperatures. The model was able to predict the pile temperature at different ambient temperatures (15, 20, 25, 30 and 35°C) and different airflow rates (0.7, 1.1 and 1.5 mg air s-1 kg-1 dry matter). The results showed that the pile temperature increases with increasing ambient temperature and it decreases with increasing airflow rates, where, as the ambient temperature increased from 15 to 35°C, the pile temperature increased from 33.40 to 37.41°C, and when the airflow rates increased from 0.7 to 1.5 mg air s-1 kg-1 dry matter, the pile temperature decreased from 34.40 to 32.39°C. The pile temperature increased slightly and reached a maximum value at day 14. It indicates that the net energy gained to the pile increases with increasing ambient temperature, meanwhile, the heat lost decreases with increasing ambient temperature. The model results indicated that the predicted daily temperature was in a reasonable agreement with those measured ones and other data in literature (Barrena et al. and Ahn et al.) at different ambient temperatures and airflow rates, where, it ranged from 30.30 to 73.40°C, while it was from 18.0 to 71.0°C experimentally during the whole period of compost maturation.

Thermal Simulation of a Dinghy Sailor

This paper describes the development of a model to simulate a dinghy sailors’ body temperature during a sailing match. This simulation has been developed as part of the master thesis by the author: “Thermal optimization of competitive sailing gear”.A literature study is done to define the human body heat balance and thermal comfort. Next a basic heat balance model was developed and simulated in MatLab Simulink. A field test was used to validate an elaborated model and recommendations are given for future work on this subject.

Process Simulation and Control Optimization of a Blast Furnace Using Classical Thermodynamics Combined to a Direct Search Algorithm

Several numerical approaches have been proposed in the literature to simulate the behavior of modern blast furnaces: finite volume methods, data-mining models, heat and mass balance models, and classical thermodynamic simulations. Despite this, there is actually no efficient method for evaluating quickly optimal operating parameters of a blast furnace as a function of the iron ore composition, which takes into account all potential chemical reactions that could occur in the system. In the current study, we propose a global simulation strategy of a blast furnace, the 5-unit process simulation. It is based on classical thermodynamic calculations coupled to a direct search algorithm to optimize process parameters. These parameters include the minimum required metallurgical coke consumption as well as the optimal blast chemical composition and the total charge that simultaneously satisfy the overall heat and mass balances of the system. Moreover, a Gibbs free energy function for metallurgical coke is parameterized in the current study and used to fine-tune the simulation of the blast furnace. Optimal operating conditions and predicted output stream properties calculated by the proposed thermodynamic simulation strategy are compared with reference data found in the literature and have proven the validity and high precision of this simulation.

Investigation of a simple approach to predict rainscreen wall ventilation rates for hygrothermal simulation purposes

Hygrothermal simulation programs are commonly used by design engineers to analyse moisture performance of building envelopes. For ventilated assemblies, programs typically require the user to enter cavity ventilation rates. If such input data are not prepared on physical grounds, it can impair the quality of the simulation results. In earlier papers: (1) estimations of ventilation rates in experimental walls based on cavity air velocity measurements; (2) comparative calculations based on monthly and annual tabular climate data, a simple driving force model and models of cavity airflow and heat balance, have been presented. In this study, the models and hourly climate field data were used to perform calculations of transient cavity ventilation rates for comparison with previous experimental results. For 13 different time periods extending from 24 to 91 h, the calculated average ventilation rates were within or very close to the experimentally estimated limits for the ventilation rate. Additionally, the calculations captured the temporal variability and the physical cause of ventilation airflow in the cavities reasonably well. The applied calculation methodology can be developed into a user friendly approach to estimate realistic ventilation rate input data for hygrothermal purposes. Limitations and possible improvements of the methodology are discussed. The influence of the accuracy and resolution of the ventilation rate input data in simulations is demonstrated in a case study.

Internal Multi-Physics Phenomena of SOFC with Direct Internal Reforming

This paper presents a detailed model to evaluate power density, species concentration, operating current/voltage, efficiency and temperature of a solid oxide fuel cell (SOFC) operating under direct internal reforming conditions. The computational framework, at the unit-cell level, encompasses a detailed 42-step reaction pathway for heterogeneous chemistry in the anode structure (Ni based catalysts), modified Butler-Volmer formalism to represent charge transfer chemistry, Dusty Gas Model for the porous media transport and a simple 1D solid-phase heat balance model. Simulations are performed for configurations ranging from simple 1D electrochemical cells to quasi-2D unit cells to complex 3D stacks, to elucidate the effectiveness of the tool for performance and design optimization.

Modeling the heat balance of a solar greenhouse with a passive heat accumulator

A model of heat balance of a solar greenhouse with a passive water accumulator in the system soil-plants-heat accumulator-air-fencing-atmosphere is presented. The heat of moisture evaporation from the soil surface and plants is defined using the Bowen-Penman method.

Lifter design for enhanced heat transfer in a rotary kiln reactor

Rotary kiln reactors are frequently equipped with an axial burner with which solid burden material is directly heated. The burner flame provides the heat required for the vaporization of the water and the reaction of the solid phase. Lifters are commonly used along the length of the system to lift particulate solids and increase the heat transfer between the solid bed and the combustion gas. The material cascading from the lifters undergoes drying and reacting through direct contact with the gas stream. In this study, volume distribution of materials held within lifters was modeled according to the different lifter configuration and appropriate configuration was used for the design purpose. This was applied to the simplified one-dimensional heat balance model of a counter-current flow reactor, which contributes to the increase of the effective contact surface, and thereby enhances the heat transfer.

Existence of an independent phonon bath in a quantum device

At low temperatures, the thermal wavelength of acoustic phonons in a metallic thin film on a substrate can widely exceed the film thickness. It is thus generally believed that a mesoscopic device operating at low temperature does not carry an individual phonon population. In this work, we provide direct experimental evidence for the thermal decoupling of phonons in a mesoscopic quantum device from its substrate phonon heat bath at a sub-Kelvin temperature. A simple heat balance model assuming an independent phonon bath following the usual electron-phonon and Kapitza coupling laws can account for all experimental observations.

On the efficient use of a lowtemperature heat source by the organic Rankine cycle

Abstract The evaporation temperature is regarded as one of the major parameters influencing the organic Rankine cycle (ORC) efficiency. Majority of contributions in literature for ORC cycle analyses treat the heat source as if it had an infinite heat capacity. Such analyses are not valuable as the resulting temperature drops of the heat source needs to be small. That leads to the fact that the heat source is not well explored and in the case of waste heat utilization it can prove the poor economics of the ORC. In the present study cooperation of the ORC cycle with the heat source available as a single phase or phase changing fluids is considered. The analytical heat balance models have been developed, which enable in a simple way calculation of heating fluid temperature variation as well as the ratio of flow rates of heating and working fluids in ORC cycle. The developed analytical expressions enable also calculation of the outlet temperature of the heating fluid.

Analysis and Improvements on the Body Heat Insulation Materials on the Basis of Cold-Chain

The cold-chain transportation industry has just started, so energy waste in cold-chain logistics is very serious. At the same time, costs got raised, resulting in profits shrinking. In this paper, measures about improving the body heat insulation material are put forward from the angle of energy consumption which is on the basis of the heat balance model of retaining structure.

The evaluation of a dynamic, mechanistic, thermal balance model for Bos indicus and Bos taurus

SUMMARYThe Thompson model (Thompson et al., in press), a heat balance model for cattle, was evaluated for Bos indicus and B. taurus under different climate conditions through the use of two local and one global sensitivity analyses and tested against independent datasets. The local analyses, which evaluate the individual effects of parameters on model output, showed that the vasodilation/vasoconstriction parameter and reference body temperature (Tbref) strongly affected body temperature. The global analysis, which evaluates the overall effect of parameters on model output, showed that 6 out of 24 parameters account for 0·79–0·89 of the model variation. The high proportion of variation accounted for by the parameters demonstrates that the model is linear in its parameters, with little interaction between the parameters.The Thompson model was tested against four independent datasets which included both B. indicus and B. taurus animals. The prediction of the relationship between skin and body temperature from the model aligned closely with the relationship in the datasets (R2 ranged from 0·55 to 0·87, mean bias ranged from 0·32 to 1·49). The prediction of sweating and respiration rates from the model aligned closely with the rates measured in the datasets (R2 ranged from 0·80 to 0·98 and 0·79 to 0·93, respectively). The delay in the diurnal body temperature variation, relative to air temperature, was more accurately predicted for cattle in the sun than for cattle in climate chambers. Given the limited datasets for construction and parameterization (both of which are described in Thompson et al., in press), the model evaluated in the current study performed relatively well compared to the literature and known biology.

Effect of building envelope on thermal environmental conditions of a naturally ventilated building block in tropical climate

This article presents the effect of envelope measures on thermal environmental conditions of a naturally ventilated building block in composite climate of India. Envelope measures such as roof U-value, wall U-value, glass U-value and glass solar heat gain coefficient, roof reflectance and two combinations of these measures (total seven cases) are analysed as recommended by National Energy Conservation Building Code-India (ECBC) through prescriptive route. Subject building is modelled and simulated using dynamic thermal simulation tool. Two approaches of thermal comfort have been used in this study such as heat balance model based on laboratory study and adaptive model of thermal comfort based on field findings. Thermal environmental conditions are evaluated based on operative temperature with and without considering the effect of thermal adaptation. This study found that comfortable temperature varies from 20.3℃ to 31.5℃ based on calculation of comfortable temperature through comfort temperature equation during winter to summer season in warm climatic conditions. This study concludes that envelope with ECBC specifications offer 60% hours under comfort state which were not comfortable with conventional practiced envelope specifications of India. The same methodology is also used to investigate the effect of ECBC envelope specifications in other climatic conditions such as hot and dry, and warm and humid climate of India. Practical applications: The thermal performance of building envelope varies from climate to climate therefore care should be taken to choose particular envelope measure. This study aims to improve comfort conditions in naturally ventilated building block considering building code with/without thermal adaptation. This research would be helpful to architects, engineers and building constructors to choose the most effective or climate responsive envelope option for better thermal environment quality of the proposed building design. Use of thermal simulation tool is also recommended to examine the effect of envelope options on thermal comfort.

Design and Analysis of the Building Environment Based on DeST Software

With the Songhua university Dust software simulation technology as a tool, and the green environment and sustainable development concept as a guide, to construct the building process heat balance model, and to put forward the state space equation method of the heat balance Selecting World Expo 2012 Yeas Korea swimming pool is a real column object, to discuss the key elements of dynamic thermal engineering design, a modern architectural design is no longer isolated, and however it is a combination of science and art, sublimation of humanity and intelligence, which is a comprehensive system design.

福島第一原子力発電所１，２，３号機の格納容器内温度評価のための熱バランスモデル構築について

福島第一原子力発電所１，２，３号機の格納容器内温度評価のための熱バランスモデル構築について