HEAT TRANSFER
CHALLENGES IN PROCESS
INTENSIFICATION
David Reay
What is Process Intensification?
In the words of chemical engineers:
 PI significantly increases transport rates
 It gives every molecule the same processing
experience
It can also lead to improved energy efficiency,
smaller & lower cost plant and safer
processing (e.g. by reduced inventories). It
can permit local production of food/chemicals.
HEXAG Relevance
Highly compact/micro-heat exchangers
 Heat exchanger- and micro-reactors
 Heat pipes
 Heat transfer enhancement

– Rotation
– Electric fields
– Mixing etc.
PI is not new
The Audiffren Singrun refrigerator of 1905
(France) used centrifugal forces to distribute the
fluid. This was SO2.
The NASA Rotating Boiler – 1950s
Heat fluxes to 257
W/sq.cm; 400 G.
Suggested >600
W/cm.sq. at 1000 G
Critical heat flux
increased compared to
1-G, but HTC similar.
The rotating air conditioning unit around the same
time – based upon a rotating heat pipe & axial flow
compressor, with evaporation in fan blades (LHS) and
liquid return via a tapering tube.
Rotex or Rotartica – Absorption
airconditioner.
Highly compact heat exchangers
The basis of HEX-reactors, with catalysts on each side.
Hundreds of channels, each needing identical feeds – here
for hydrogen production.
Toshiba mobile phone
100 mW direct methanol fuel cell (2005) – where
micro heat exchanger/reactor technology is needed.
Spinning disc reactor
Rotation to 10,000 rpm;
used for food processing
& chemical reactions.
Needs to deal with very
rapid exo- or
endothermic processes
on the top surface.
SDR Wave formation – strong mixing
in a thin film
SDR Temperature distribution
Uniform/isothermal heating
of treacle!
Thermal control on an SDR
Overall U of 10 kW/sq.m.K – transfers 39 kW from a 0.5
m diameter disc with a 20 K temperature difference, even
for organic fluids.
Custard manufacture
Milk & custard powder
are introduced onto the
centre of the SDR –
continuous production is
feasible.
Spinning cone is a
variant – in this case
to make barium
sulphate. Nano
particle productions
is done in China.
Plasma or laser reactors
Ceramic micro-heat exchanger
Basis of high
temperature
reactions – still
fabrication
problems. Scale
in cm.
The Honeywell Hymatic IR Detector
Cooler
Metal mesh heat exchanger. Camb.
Univ.
Cross-flow configuration here, with cooling flow
horizontal. Pressure to compact the mesh layers.
Mesh performance data for
air & water (LFM = lattice
frame material)
Taylor-Couette flows
between two closely spaced
cylinders, one of which
rotates. Laminar flow –
used for reactions.
It does throw up the question
over whether the use of bulk
fluid properties such as
viscosity are appropriate in
such equipment – the same
question hangs over flow
and heat transfer in microchannels.
Heat spreading in reactors – 6%
yield increase in China
The ‘ARCTIC’ chip cooler
Wankel-type rotary compressor; 25 mm x 30 mm
footprint; COP 4.6; 45 W duty; 40 K temp.diff.; 1000
rpm compressor speed.
A laptop – like the earlier mobile
phone!
The chip still needs cooling, as well as the
thermal control of the fuel cell reformer. The
methanol supply is shown temporarily fitted to
the laptop. (NEC)
Capillary-pumped loop for chip
cooling
130 W duty;
passive
Finally - Ashe-Morris complex
geometries
Variable channels &
agitated cells as reactor
bases.