Alternate Drying Washing Machine

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Inflatable air bag

Alternate drying mechanism in automatic
washing machine

Product Design Lab 1
Group 5

Pre-requisites







Easy operation
Safe
Greater power and water efficiency
Reasonably priced
Substantial drying of clothes
Minimal wear of clothes

Patented in 1957, the
mechanism alongside
uses a mechanical piston to
squeeze water
out of the clothes

Brainstorming & categorization of modules
Mechanical

Thermal

Chemical

Electrical

Mechanism similar to
iron pressing

Blasting hot air on the
clothes

Reducing surface
tension of water to
enable faster drying

Electrostatic attraction
of water molecules

Using vacuum (or low
pressure) for suction
of water

Blowing a vortex of
warm dry air

Using deliquescent
materials for
absorption of water

Rotation at higher
rpm
Using inward
mechanical pressure
on clothes in the form
of plates

Concept Screening
Idea

Spatial
feasibility
(fitting)

Financial
feasibility

Feasibility
with energy

Theoretical
feasibility

Manufacturing
feasibility

Efficiency

Summing
Up

Iron pressing

(-)

(-)

(-)

(-)

(-)

(-)

-6

Electrostatic
attraction

(+)

(0)

(+)

(-)

(0)

(0)

+1

Reducing
surface
tension

(+)

(0)

(+)

(0)

(-)

(0)

+1

Vacuum

(-)

(-)

(-)

(-)

(0)

(0)

-4

Deliquescent
materials

(+)

(0)

(0)

(-)

(0)

(0)

0

Hot air blast

(0)

(0)

(0)

(+)

(+)

(+)

+3

Rotation at
higher rpm

(+)

(0)

(0)

(-)

(+)

(+)

+2

Mechanical
pressure by
plates

(0)

(+)

(+)

(0)

(-)

(-)

0

Vortex of
warm dry air

(+)

(-)

(0)

(-)

(0)

(+)

0

Concept Selection
• Mimicking squeezing action using
Mechanical Pressure
• Hot Dry Compressed Air to absorb
moisture content (provided via
compressor)

Higher
RPM

Applying
pressure

Dry hot air

• Coupling existing technology for better
results due to aligning radial forces
• Use of bag with pores/holes for both,
applying pressure and passage of dry
air.

The Air Bag
Concept

Flow Rate Calculations


dm/dt = C*Y*A2 *root(2p(P1 – P2 ))
Here ,

C= orifice flow coefficient, dimensionless
A2 = cross-sectional area of the orifice hole, m² (=1mm3 )
P1=fluid pressure inside, Pa with dimensions of kg/(m·s² ) (=137 kPa =1.3 atm) P2 =fluid pressure outside,Pa (=101 kPa = 1 atm)
Y= expansion factor
p=density of air inside
Putting Y in the above equation and substituting p using real gas equation



Q= C*A2 *root{(2*Z*R*T/M)*(k/(k-1))[(P2/P1)2/k-(P2/P1)(k+1)/k]} Here,
Q=volume flow rate through the orifice as seen from the inside k= specific heat ratio (Cp/Cv), dimensionless (=1.4)
M=the air’s molecular mass, kg/mol (=28.97)
Z= the gas compressibility factor at T and P1, dimensionless (=0.9998) T=inside temperature (=323 K)

The values given in brackets were used to get the flow rate Q =0.00011 m3/s =0.66 l/m
http://en.wikipedia.org/wiki/Orifice_plate

Ref:

The Compressor
Flow rate through one orifice:
Q =0.66 l/m

The Air Bag
Pre-requisites:
1] Strength
3]elasticity

2]pliability
4]waterproof

Compressor specs:
• 66 to 75 L/m
• 1.3 to 1.5 atm
• 19.11-22.05 psi
Power :
Cost :

50W-450W
Rs.1000-1500

Perforated Tarpaulin
Apart from the above, tarpaulin
• Has high tear strength
• Can withstand high temperatures

Piping and
Connections
• PVC will not allow the hot air
to cool quickly enough to
condense the water in the
compressed air.

The Motor
• AC compound motor
• Lack of any gears
• Pulley system used

• Maximum 10% pressure drop
through the entire system
• Smooth long radius elbows
• Pipe diameter = 1 inch ; for air flow of around 4 CFM
• Motor shaft :
• Compressor shaft :

around 0.6 ‘’ diameter
around 1’’ diameter

Power : 50W-450W
Cost : Rs.1000-1500
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