Heating of Heating of WaterWaterby the by the

ComeniusgroupComeniusgroup

ofof

Merianschule Merianschule SeligenstadtSeligenstadt

April 2008April 2008

Why Water?Why Water?

•All Life on earth is based on WaterAll Life on earth is based on Water

•Water occupies special Water occupies special characteristics regarding our characteristics regarding our climatic conditionsclimatic conditions

•We use heated Water as carrier We use heated Water as carrier for heat, for cooking, for washing, for heat, for cooking, for washing, in the bathroom, for drinking, etc.in the bathroom, for drinking, etc.

Special Properties of Special Properties of WaterWater

• Solid Water (Ice) swims on the surface of Solid Water (Ice) swims on the surface of the liquid Waterthe liquid Water

• For a Dihydrogen compound of the 6th For a Dihydrogen compound of the 6th maingroup it has notable high melting and maingroup it has notable high melting and boiling points as well as a high viscosityboiling points as well as a high viscosity

• Wide gap between melting and boiling Wide gap between melting and boiling point (100°C) point (100°C)

(NH(NH33: 45°; HCl: 30°; HBr 21°; HI: 16°; CO: : 45°; HCl: 30°; HBr 21°; HI: 16°; CO: 8°)8°)

• Extremly high heat capacity of 4,18 kJ/kg Extremly high heat capacity of 4,18 kJ/kg °C°C

Effects of High Heat Effects of High Heat capacitycapacity

• High power requirement for heating High power requirement for heating

• Excellent carrier for the transport of Excellent carrier for the transport of Energy (liquid and steam)Energy (liquid and steam)

• Water is balancing the world‘s climatic Water is balancing the world‘s climatic system because of its huge volume in system because of its huge volume in the oceans and the steam in the the oceans and the steam in the atmosphereatmosphere

• Ensures only small fluctuations in Ensures only small fluctuations in global temperatures–global temperatures–

the basis for all life on our planetthe basis for all life on our planet

Heating of Water at Heating of Water at HomeHome

• Three methods are common:Three methods are common:

- electric kettle- electric kettle

- cooker- cooker

- - microwavemicrowave

Generell Aspects of Generell Aspects of Measurement and Efficiency of Measurement and Efficiency of ConversionConversion• Heating of a defined amount of WaterHeating of a defined amount of Water

• Measurement of temperature differenceMeasurement of temperature difference

• Definition of electrical parameters and Definition of electrical parameters and timetime

Two Calculations

1.) Calculation of the 1.) Calculation of the inserted Energyinserted Energy

Voltage x Amperage = PowerVoltage x Amperage = Power

(in Watt)(in Watt)

Power x Time = Energy inputPower x Time = Energy input

(in Joule or Wattseconds)(in Joule or Wattseconds)

2.) Calculation of the 2.) Calculation of the absorbed Energyabsorbed Energy

Weight of Water x heat Capacity x Weight of Water x heat Capacity x

temperature differencetemperature difference

==

Absorbed EnergyAbsorbed Energy

(in Joule or Wattseconds)(in Joule or Wattseconds)

Efficiency of the SystemEfficiency of the System

absorbed energyefficiency

inserted energy

Experimental SetupExperimental Setup

Measured EfficiencyMeasured Efficiency

electric electric cookercookermicrowavemicrowave

kettlekettle

92% 87% 47%

Pros and Cons Pros and Cons

+ most efficient Method (92% + most efficient Method (92% conversion)conversion)

+ only small amount of the vessel is + only small amount of the vessel is heatedheated

- Constructed for of heating water only- Constructed for of heating water only

Electric kettle:

Pros and ConsPros and Cons

+ reasonably efficient method (87% + reasonably efficient method (87% conversion)conversion)

+ wide range usage+ wide range usage+ time saving because of high power+ time saving because of high power+ best method for long operating times and + best method for long operating times and

large amountslarge amounts- hotplate and vessel need to be heated - hotplate and vessel need to be heated

additionallyadditionally- Residual heat is often not used- Residual heat is often not used

Cooker:

Pros and Cons of the Pros and Cons of the methodsmethods

+ direct warming without heating of the + direct warming without heating of the vesselvessel

+ short start-up time+ short start-up time

+ best method for short-time heating+ best method for short-time heating

- only 47% of the inserted energy is used- only 47% of the inserted energy is used

Microwave:

How Processes WorkHow Processes Work