Czech Technical University in Prague Faculty of Civil Engineering Department of Microenvironmental and Building Services Engineering

Heating systems Apllied thermodynamics Indoor environment

2008/2009

Michal Kabrhel

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Heating n

The function Heat supply to guarantee required indoor temperature n Heat supply for technology n Heat supply for hot water generation n

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The principle

Michal Kabrhel

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Heating - History 700 BC - 0

Hypocausta

Michal Kabrhel

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Heating - History – Middle Ages n

Fireplace, stove

BEE1 Michal - prof.Kabele Kabrhel

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Heating - History 18th-19th century - steam system

Michal Kabrhel

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Heating - History 20thcentury

Michal Kabrhel

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th 20 century

History warm water systems Steam systems are replaced by warm water ones - use of electricity, pumps, control

Michal Kabrhel

Warm water boiler Strebl 1927

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1900-1945

Michal Kabrhel

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Heating nowadays n n n n

Warm water systems Gas boilers operated by electronics Heating surface inside floor, wall, ceiling Computer models

Michal Kabrhel

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Heating nowadays

Michal Kabrhel

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Applied thermodynamics n

Heat, heat energy n

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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 n

State variable describing kinetics energy of the particles of the system n n n

2008/2009

Thermodynamic /Kelvin/ T [K] Celsius t [°C] t= T-273,15 Fahrenheit [°F] 1°F=5/9°C (°F-32).5/9=°C

Michal Kabrhel

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Basic laws of thermodynamics n

Zeroth law n

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2008/2009

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).

Michal Kabrhel

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Basic laws of thermodynamics n

1.law n

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2.law n

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The total energy of the system plus the surroundings is constant. (internal energy of system) The second law is concerned with entropy (S), which is a measure of disorder. The entropy of the universe increases.

3.law n

2008/2009

It is impossible to cool a body to absolute zero by any finite process

Michal Kabrhel

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Heat transfer modes n

Heat Conduction n

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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. n Newton-Richman, Fourier-Kirchhof n

2008/2009

Michal Kabrhel

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Heat transfer n

Transmission convection+conduction+convection

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Radiation n Electromagnetic waves

2008/2009

Michal Kabrhel

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Indoor environment

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Theory of the indoor environment n n n n n

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Hygrothermal microclimate Acoustic microclimate Psychical microclimate Light microclimate Electrostatic microclimate

Hygrothermal microclimate n

2008/2009

Indoor environment state from the viewpoint of thermal and moisture flows between the human body and surroundings

Michal Kabrhel

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Heat Exchange between the Human Body and the Enviroment n

Metabolic Rate M n n n

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n n n n

T p

Heat loss Q n

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degree of muscular activities, environmental conditions body size.

T

Respiration Convection Radiation Conduction Evaporation

a

Body thermal balance equation

2008/2009

M=Q comfort M>Q hot M50