Modelling (pre-)Design Activities With a Multi-Stakeholder Perspective - Principia Designae: Pre-Design, Design, and Post-Design - page 182

Requirements
definition

V:
Ne i ! Re i

Kettle capacity sufficient to prepare four cups of
tea/coffee

Volume capacity ¼1 L V:

Ne i ! Re i

VI:
Re i ! Re

Volume capacity ¼1 L Volume capacity ¼1 L VI:

Re i ! Re

Height of the kettle < 300 mm

VII:
Re ! R i

Height of the kettle < 300 mm Height of the kettle < standard scaffolds height VII:

Re ! R i

VIII:
R i ! F i

Volume capacity ¼1 L Kettle contain water VIII:

R i ! F i

IX:
R i ! Re i

Subsequent usages of the kettle do not create variations
of the boiling time, as well as in the chemical/physical
or organoleptic features of water

After 1,000 usages of the kettle the boiling time to heat
1 L of water should remain less than 3 min

IX:
R i ! Re i

The hardness of water boiled in the kettle should not
increase more than 5 mg/L, nor the poured water
should contain particles bigger than 0.2 mm

FBS
formulation

XI:
Re ! R i

Boiling time < 3 min Heating time of 1 L of water from 15 to 100 C < 3 min XI:

Re ! R i

XII:
R i ! F i

Heating time of 1 L of water from 15 to 100 C < 3 min The kettle increases water temperature from 15 to

100

XII:
R i ! F i C

XIII:
R i ! B i

Heating time of 1 L of water from 15 to 100 C < 3 min The kettle supplies through an electric resistance 356 kJ

to water (by Joule effect) in less than 3 min

XIII:
R i ! B i

XIV:
R i ! S i

Heating time of 1 L of water from 15 to 100 C < 3 min The kettle parts in contact with water must be made with

materials capable of working at 100

XIV:
R i ! S i C