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Czech Technical University in Prague Faculty of Civil Engineering Department of Microenvironmental and Building Services Engineering Czech Technical University in Prague Faculty of Civil Engineering Department of Microenvironmental and Building Services Engineering SE20 – Heating systems Lecture 1 Introduction Introduction Doc.Ing.Karel Kabele,CSc. Room: A122 kabele@fsv.cvut.cz

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

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

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Historie – medieval age Stoves, fireplaces Stoves, fireplaces

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History 18-19.century steam

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

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

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Applied thermodynamics Heat, heat energy 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. 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 Temperature State variable describing kinetics energy of the particles of the system State variable describing kinetics energy of the particles of the system Thermodynamic /Kelvin/ T [K] Thermodynamic /Kelvin/ T [K] Celsius t [°C] t= T-273,15 Celsius t [°C] t= T-273,15 Fahrenheit [°F] 1°F=5/9°C (°F-32).5/9=°C Fahrenheit [°F] 1°F=5/9°C (°F-32).5/9=°C

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Basic laws of thermodynamics Zeroth law Zeroth law There is a state variable TEMPERATURE. Two systems at the same temperature are in thermodynamics equilibrium. 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). 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).

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

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

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Heat transfer Transmission convection+conduction+convection Transmission convection+conduction+convection Radiation Radiation Electromagnetic waves Electromagnetic waves

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

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Heat Exchange between the Human Body and the Enviroment Metabolic Rate M Metabolic Rate M degree of muscular activities, degree of muscular activities, environmental conditions environmental conditions body size. body size. Heat loss Q Heat loss Q Respiration Respiration Convection Convection Radiation Radiation Conduction Conduction Evaporation Evaporation Body thermal balance equation Body thermal balance equation M=Q comfort M>Q hot M
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Factors Influencing Thermal Comfort Human Human Metabolic Rate Metabolic Rate Clothing Insulation Clothing Insulation Space Space Air Temperature (Dry-Bulb) Air Temperature (Dry-Bulb) Relative Humidity Relative Humidity Air Velocity Air Velocity Radiation (Mean Radiant Temperature) Radiation (Mean Radiant Temperature)

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Environmental indices Operative Temperature Operative Temperature where t g = operative temperature where t g = operative temperature t a = ambient air temperature t a = ambient air temperature t r = mean radiant temperature t r = mean radiant temperature h c = convective heat transfer coefficient h c = convective heat transfer coefficient h r = mean radiative heat transfer coefficient h r = mean radiative heat transfer coefficient

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Environmental indices Mean Radiant Temperature Mean Radiant Temperature where where tr = mean radiant temperature tr = mean radiant temperature Ti = temperature of the surrounding surface i, i=1,2,....,n Ti = temperature of the surrounding surface i, i=1,2,....,n φ rn = 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 φ rn = 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

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Measuring instruments

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

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