Proposed Experimental Testing

In order to propose the experimental testing parameters it is first necessary to define the calculation method. This will enable assessment of SI units in which to test, if the composite can regulate thermal conductance. The calculation is in fact two. The reasoning for this, all materials have a capacity to absorb energy as determined by specific heat capacity cp. This thermal capacity is dependent upon heat transfer q. To enable regulation of q, the method of applying vascular networks as inspired by nature uses fluidics. Hence, fluids are dependent upon mass flow rate and specific heat capacity of the fluid to absorb and transfer thermal energy. The differential temperature of the input fluidic temperature and output fluidic extract can measure the absorption rate, delta t.

This will determine the heat absorption by the fluid in response to solar radiation. By the calculation method of :

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However, any fluid within a channel network in nature (plants and cardiovascular, the human body) and man-made fluidic systems, all are affected by fluidic flow directional movement. Resistance to flow within a fluidic network defines this movement and this can be described by pressure. Pressure is a measure of the resistance to flow and this will impact on the fluidic absorption rate.

The Pressure Resistance to fluidic flow within the fluidic network calculation is: qH = ˙m Cp  ∆t   

q

△t

˙

m

Q   

Heat Capacity

Pressure drop between inlet and export stem vasculature

Fluidic Flow

The laboratory testing of the prototype is not focused upon thermal conductivity but the absorption of solar (ie non-thermal) IR, which then will heat up the polymer device. Transition temperature of the polymer will be characterized by modulating microfluidic based flow in steady state. This capture of energy by solar modulation will progress a thermal function polymer as an IR radiation stop band with lower phase transition temperature. These properties will be measured by laboratory testing and this is described below as a series of step stages.

Structural Assembly of the Polymer Device: Two plates of 5mm polymer form the prototype device. The base plate contained the microchannel network that is fabricated by laser cutting into the surface of the base plate. This channel geometry will contain the microfluidic based flows. The polymer counterplate acts as the solar radiation absorber pane. These two plates have been bonded together to form the structural assembly-testing device, shown in Figure 5.4. The justification of the geometry network, to develop a multi microchannel formation is determined in Chapter 6, Section 6.6: Network Geometry Evolution. Two plates of PMMA 5mm thick were cut to a dimensional size of 158mm width and length 220mm. One of the plates was inscribed , through laser application to fabricate a geometry arrangement of micro channels. These channels formed the volumetric areas of water contained within the depth of the plate. This geometry formation plate was resin bonded to the remaining counter plate to assemble the microfluidic device.

Figure 5.4 PMMA Composite Device (by author), dimensions in mm.

Using a microfluidic platform of steady state flow in cross slot channels by precise flow rate in the device enhances fluid to material (transparent polymer) heat transfer for thermal energy capture and storage. Optimization is determined by microchannels hierarchical order regulated by rules of minimum energy loss, minimum effective power flow rates and minimum pressure drop. The controlling process of a thermally functional microfluidic

solar radiation and this is determined through pressure equalization within a closed loop network. Resistance is the parameter to enhance modulating flow rates optimization to manipulate thermal heat transfer, to evaluate this. These characteristics are exhibited in the uniform spacing patterns of hierarchical sequence vascularization patterns (veins) in advance leaf species.

Heat Conductivity Regulation by Fluidic Thermal Exchange: The absorption of solar IR in the PMMA counterplate will heat up. The introduction of the microvasular channel network will enable a liquid to circulate and interact with material temperature regions of the device. This liquid encapsulated within the channels acts as an absorber of thermal temperature. Hence the channel network within the device will be connected to a fluidic source to enable this heat exchange interaction by fluidic import and export measures, shown in Figure 5.5.

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Figure 5.5 Fluidic Connection Input into the Vascular Channel Network (by author)

Fluidic Flow: The inlet port tube is attached to the device. However, fluidic pressure feed is required to create volume liquid flow within the device, shown in Figure 4.4. This pump introduces pressure via fluidic flow through the channel network geometry and the outlet port will enable removal. The establishment of pressure, measurement of flow rate and fluidic extract temperature can then be defined. This syringe pump will have a large fluidic reservoir to pump water into the device to create the flow and maintain this flow rate. Thermocouples temperature sensors undertake temperature monitoring of fluidic absorptivity, shown in Figure 5.6.

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Figure 5.6 Fluidic Flow and Temperature Fluid Monitoring (by author)

Introduction of a Heat Source: The transparent polymer is subjected to an artificial solar (incandescent light) source that emitted IR wavelength 1000 watts per m2_{. Solar heat load increase the surface temperature of the polymer}

surface pane. Distilled water is be pumped through the channel network that directed the structural assembly of the polymer. The fluidic input and extract temperature into the manifolds channel was monitor by thermocouples. Switching of the water flow for solar IR absorption regulates the heating effect from the panes. Sensors monitored material–fluid thermal interface transport exchange. A thermal infrared IR camera will obtain these measurements. This analysis will enable assessment of thermal switching to manipulate PMMA material phase transmission temperature. Figure 5.7 illustrates the schematic of the experimental testing design.

Figure 5.7 Experimental Design Testing Schematic (by author - note no photography of this experiment was allowed, due to the secure facility where the testing took place)

The value of this experimental testing design will assess thermal switching selectivity for IR to material regions. Laboratory Test to assess photo type composite by experimental testing: A syringe pump will be used to control the

distilled water solution flow within the composite epoxy. A 1000W incandescent light will be placed above the composite material approximately 80 cm away as a heat source to the composite material, an initial temperature of 35 increasing to a maximum of 40 C. Thermocouples will be used to assess fluidic input and extract temperatures. There are limitations imposed on this test and these are reviewed in Chapter 8, Section 8.4: Review of Limitations and Constraints. However, there is one particular limitation to highlight here, which is the time period of the experiment itself. All syringe pumps are used in experimental testing to establish precise fluidic flow rate of a fixed volume of water in microchannel use tank reservoir. These reservoirs contain a fixed volume of water to determine the flow rate (pumping pressure) through the multi microchannel network. The fixed volume of water at a predetermined flow rate within a network is determined by time, through water volume reservoir capacity. This establishes the time frame, and duration of the experiment, at 50 minutes. Temperature monitoring greater than 50 minutes could not be achieved by the syringe pumps reservoir fixed water capacity. This time frame is therefore a limitation of the research.

5.10 Conclusion

Nature’s biological systems are living multifunctional mechanical information systems of chemical composition. They have the ability to learn and adapt to changing climatic conditions by self-regulation of solar absorption, to achieve

thermal management. To embed this functions into a polymer to advance a transparent material as an energy capture and storage system. Through the process of flow, pressure, heat transport by real-time reactions by precision hydrodynamics control as defined by a leaf is new.

Bio-inspired solution to progress from a static IR absorber , a mere material entity, to a dynamic one to interact with the environment of real time performance change by the hour, season and weather conditions as a energy flow cycle. The following chapter 6 defines natures leaf vasculature formations to evolve material function as a thermal flow system aligned and oriented to thermal monitoring temperature with time through optimisation of capillary channels geometry networks.