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Heat Balance of Horizontal Ground Heat Exchangers

Abstract

This work refers to the modelling of heat transfer in horizontal ground heat exchangers. For different conditions of collecting heat from the ground and different boundary condition profiles of temperature in the ground were found, and temporal variations of heat flux transferred between the ground surface and its interior were determined. It was taken into account that this flux results from several different mechanisms of heat transfer: convective, radiative, and that connected with moisture evaporation. It was calculated that ground temperature at great depths is greater than the average annual ambient temperature.

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Maize transpiration in response to meteorological conditions

Sciences, 30, 491-507. Gao Y., Duan A. W., Qiu X. Q., Zhang J. P., Sun J. S., Wang H. Z., 2010: Plant transpiration in a maize/soybean intercropping system measured with heat balance method. Chinese Journal of Applied Ecology, 21, 1283-1288. Gavloski J. E., Ellis C. R., Whitfield G. H, 1992: Effect of restricted watering on sap flow and growth in corn (Zea mays L.). Canadian Journal of Plant Science, 72, 361-368. Gerdes G., Allison B. E., Pereira L. S., 1994: Overestimation of soybean crop transpiration by sap flow

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24-Hour Microclimate Conditions in Livestock Building

Abstract

The size of all sensible heat balance components in livestock building varies in time, because it depends on time-varying weather factors. On the example of two buildings, sensible heat balance was shown on a daily basis. Measurements carried out in winter and spring in two livestock buildings with usable attics included measurements of air temperature and humidity inside and outside, air velocity in ventilation channels, and wind speed. Measuring devices were designed to record the results of measurements at intervals of 300s. During each such time interval, sensible heat losses by ventilation, heat losses by permeation through the barrier construction, and the amount of sensible heat produced by the animals were calculated. The results of measurements were shown in graphs. The study is important for the development of animal livestock building.

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Principles of the New Universal Thermal Climate Index (UTCI) and its Application to Bioclimatic Research in European Scale

REFERENCES Blażejczyk K., 1994, New climatological- and -physiological model of the human heat balance outdoor (MENEX) and its applications in bioclimatological studies in different scales, Zeszyty IGiPZ PAN , 28: 27-58. Błażejczyk K., 2004, Bioklimatyczne uwarunkowania rekreacji i turystyki w Polsce (Bioclimatic principles of recreation and tourism in Poland), Prace Geograficzne , Instytut Geografii i Przestrzennego Zagospodarowania (IGiPZ) PAN, 192. Fiala D., Lomas K.J., Stohrer M., 1999, A computer model of human thermoregulation for a

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The Effect of Atmospheric Electromagnetic Radiation on an Opened System

Abstract

In opened systems with liquid-phase (for example open-source bioreactors for various purposes) very significant temperature can be generated. The operation of the system can be impaired, possibly completely inhibited (too low, too high temperature values). The analytic description of the operation’s heat flow is needed to achieve the optimized operation and to block the thermodynamic inhibition. The aim is to examine the inner system opportunities and the auxiliary energy. The estimates values quantify the effects of atmospheric electromagnetic radiation on opened systems. Based on the developed model by increasing the complexity of the method, it is appropriate to describe the heat flow of opened systems and to explore the energy integration possibilities.

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Water temperature in investigations of Polish lakes

jezior (na przykładzie Jeziora Górnego Raduńskiego) (From studies on the thermic conditions and heat balance of the lakes), Zesz. Nauk. UGdań. Geogr. 3: 81–97 (in Polish, English summary). Lange W., 1978, Warunki akumulacji ciepła w jeziorach Pojezierza Kaszubskiego (Conditions of heat accumulation in the lakes of the Cassubian Lake District), Zesz. Nauk. UGdań. Geogr. 8: 89–108 (in Polish, English summary). Lange W., 1985a, Ustroje termiczne jezior Pojezierza Kaszubskiego (Thermical regimes of Cassubian Lake District lakes), Zesz. Nauk. UGdań. Geogr. 13

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Mathematical modelling of wet oxidation of excess sludge

Mathematical modelling of wet oxidation of excess sludge

A mathematical model enabling a quantitative description of wet oxidation of excess sludge in continuous bubble columns is proposed. The model consists of mass and heat transfer kinetic equations and material and heat balance equations of gas and liquid phases flowing through the absorber. The equations of material and heat balance refer to a parallel, co- current flow of gas and liquid phase and take into account a complex chemical reaction in the liquid phase core. The proposed model was used in a numerical simulation of wet oxidation in a bubble absorber for different process conditions: flow rate and composition of the gas and liquid phase, temperature and pressure, and different heights and diameters of the column.

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Comparative study of Time Optimal Controller with PID Controller for a Continuous Stirred Tank Reactor

Abstract

Continuous Stirred Tank Reactor (CSTR) is the productive part in different chemical and process industries, and hence there is a need to control this process at desired optimum conditions of temperature and concentration. This paper deals with modelling and constrained control of a CSTR that minimises the processing time. Modelling consisted in performing the mass and heat balances of the CSTR system. Different controllers (time optimal, PID) were then applied to this non-linear system and compared within the boundaries of the control input and states. A theoretical case study was solved numerically using the orthogonal collocations method and simulations, resulting in a comparison of different controllers.

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Optimisation of Combined Cycle Gas Turbine Power Plant in Intraday Market: Riga CHP-2 Example

Abstract

In the research, the influence of optimised combined cycle gas turbine unit – according to the previously developed EM & OM approach with its use in the intraday market – is evaluated on the generation portfolio. It consists of the two combined cycle gas turbine units. The introduced evaluation algorithm saves the power and heat balance before and after the performance of EM & OM approach by making changes in the generation profile of units. The aim of this algorithm is profit maximisation of the generation portfolio. The evaluation algorithm is implemented in multi-paradigm numerical computing environment MATLab on the example of Riga CHP-2. The results show that the use of EM & OM approach in the intraday market can be profitable or unprofitable. It depends on the initial state of generation units in the intraday market and on the content of the generation portfolio.

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Development of a Simulation Model for Controlling and Improving the Productivity of Batch Reactors

This paper describes the development of a dynamic simulator model for a jacketed batch reactor equipped with a mono-fluid heating/cooling system. The Mono-fluid flows at constant flow-rate through the jacketed reactor. The heating and cooling are assured respectively by electrical resistance and two plate heat exchangers. A detailed description of the equations leading to the development of simulation model is presented. The model is based on writing the equations of the mass balance and the heat balance for the reactor and the thermal loop in unsteady state. To validate the simulation model, we first studied the thermal behavior of the reaction mixture during heating and cooling, using water as the reaction mixture. We then considered the consecutive chemical reaction of the synthesis of cyclopentanediol from cyclopentadiene by studying the yield of this reaction. The results show that heating the reaction mixture increases significantly the yield of this synthesis reaction.

Open access