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SE20 – Heating systems

SE20 – Heating systems. Doc.Ing.Karel Kabele,CSc. Room: A122 kabele @fsv.cvut.cz. Lecture 1 Introduction. Lectures schedule. 1 The built environment. Applied thermo mechanics. 2 MULCOM 3 Heat loss and consumption calculations. Principles of heating equipment.

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SE20 – Heating systems

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  1. SE20 – Heating systems Doc.Ing.Karel Kabele,CSc. Room: A122 kabele@fsv.cvut.cz Lecture 1 Introduction

  2. Lectures schedule 1 The built environment. Applied thermo mechanics. 2MULCOM 3 Heat loss and consumption calculations. Principles of heating equipment. 4 Heat emitters, space heating 5 (Easter Monday) 6Heating systems 7 Heating systems 8 Boilers, boiler plants 9 Heat exchangers, district heating 10 Renewable sources, combined heat and power plants 11 Safety device for central heating systems 12 Pumps in heating systems 13 Hot water generation 14 Heating system control, building energy management systems

  3. History 700 B.C. - 0 Hypocausta Greece, Italy, Turkey

  4. Historie – medieval age • Stoves, fireplaces

  5. History 18-19.century steam

  6. History 20.centuryhot-water systems Electricity, Water systems Cast-iron boilers Coal, Gas Boiler Strebl 1927

  7. Present and future? • Warm water systems • Gas boilers controled by microprecessor • Heat emmitters located in the floor, walls and ceiling • Computer modelling and simulation

  8. Applied thermodynamics • Heat, heat energy • Heat is the energy transferred between a system and its surroundings due solely to a temperature difference between the system and some parts of its surroundings. • Temperature • State variable describing kinetics energy of the particles of the system • Thermodynamic /Kelvin/ T [K] • Celsius t [°C] t= T-273,15 • Fahrenheit [°F] 1°F=5/9°C(°F-32).5/9=°C

  9. Basic laws of thermodynamics • Zeroth law • There is a state variable TEMPERATURE. Two systems at the same temperature are in thermodynamics equilibrium. • The zeroth law of thermodynamics states that if for example you have a Body (A) and a Body (B), both at the same temperature; and then you have a Body (C) which is at the same temperature as Body (B); Therefore the temperature of Body (C) is equal to the temperature of Body (A).

  10. Basic laws of thermodynamics • 1.law • The total energy of the system plus the surroundings is constant. • 2.law • The second law is concerned with entropy (S), which is a measure of disorder. The entropy of the universe increases. • 3.law • It is impossible to cool a body to absolute zero by any finite process

  11. Heat transfer modes • Heat Conduction • Heat is transferred between two systems through a connecting medium, Biot-Fourier • Heat Convection • Macroscopic movement of the matter in the forms of convection currents. • Newton-Richman, Fourier-Kirchhof

  12. Heat transfer • Transmission convection+conduction+convection • Radiation • Electromagnetic waves

  13. Indoor environment • Theory of the indoor environment • Hygrothermal microclimate • Acoustic microclimate • Psychical microclimate • Light microclimate • Electrostatic microclimate • Hygrothermal microclimate • Indoor environment state from the viewpint of thermal and moisture folws between the human body and surroundings

  14. Tp Ta Heat Exchange between the Human Body and the Enviroment • Metabolic Rate M • degree of muscular activities, • environmental conditions • body size. • Heat loss Q • Respiration • Convection • Radiation • Conduction • Evaporation • Body thermal balance equation M=Q comfort M>Q hot M<Q cold

  15. Factors Influencing Thermal Comfort • Human • Metabolic Rate • Clothing Insulation • Space • Air Temperature (Dry-Bulb) • Relative Humidity • Air Velocity • Radiation (Mean Radiant Temperature)

  16. Environmental indices • Operative Temperature • where    tg = operative temperature •             ta = ambient air temperature •             tr = mean radiant temperature •             hc = convective heat transfer coefficient •             hr = mean radiative heat transfercoefficient

  17. Environmental indices • Mean Radiant Temperature • where    • tr = mean radiant temperature • Ti = temperature of the surrounding surface i, i=1,2,....,n • φrn = shape factor which indicates the fraction of total radiant energy leaving the clothing surface 0 and arriving directly on surface i, i=1,2,...n

  18. Measuring instruments

  19. Thermal comfort evaluation • PMV index (Predicted mean vote) • PPD index (Predicted percentage of dissatisfied)

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