![Figure 7. Comparison of present work with that of Wibulswas [5] for = 4.](/figures/figure-7-comparison-of-present-work-with-that-of-wibulswas-5-cm76pld3.webp)
![Figure 8. Comparison of present work with that of Perkins et al. [14] and Chandrupatla and Sastri [15] for = 1.](/figures/figure-8-comparison-of-present-work-with-that-of-perkins-et-115pkppo.webp)
Q2. Why are microchannel heat sinks of particular interest?
Microchannel heat sinks are of particular interest due to the very high rates of heat transfer they enable in conjunction with greatly reduced heat sink length scales and coolant mass.
Q3. What is the simplest way to predict the thermal performance of microchannels?
Numerical simulations based on the finite volume method were conducted to predict steady, laminar heat transfer coefficients in hydrodynamically developed but thermally developing flow.
Q4. How long does the thermal entrance length in a rectangular channel be?
The dimensionless thermal entrance length, * thz , defined as the distance required over which the localNusselt number, Nuz, drops to 1.05 times the fully developed value, Nu [11], can be determined from the results.
Q5. What is the way to simplify the conjugate analysis?
They concluded that the H1 thermal boundary condition is the most appropriate for simplified analyses, when full conjugate analyses are not affordable.
Q6. What is the effect of unequal heat addition on adjacent sides of rectangular channels?
Svino and Siegel [13] investigated the effect of unequal heat addition on adjacent sides of rectangular channels and found that poor convection due to low velocities in the corners and along the narrow wall causes peak temperatures to occur at the corners.
Q7. What is the appropriate computational domain for the full three-dimensional conjugate analysis?
To simplify the full three-dimensional conjugate analysis, the computational domain has typically been restricted to include only the fluid region, with one of the following alternative thermal boundary conditions applied to the channel walls: H1 (circumferentially constant wall temperature and axially constant wall heat flux), H2 (uniform wall heat flux, both axially and circumferentially), and T (uniform wall temperature, both axially and circumferentially) [8].
Q8. What is the velocity profile of a rectangular duct?
As the flow is assumed to be hydrodynamically fully developed, the following exact analytical solution by Marco and Han [10] for the fully developed velocity profile in a rectangular duct is used as the inlet condition: 216 2 ( , , 0)21 / 2 1 cosh /1 cos 3 cosh / 21, 3, ...b dpu x y dzn n y b n xn a b bn n (2)in which the pressure gradient dp/dz is given in terms of the mean fluid velocity, um, by 25 51,3 ,...1 192 1 1 tanh 3 2 2 mndp b n a udz a n bb (3)Figure 2 shows such a fully developed velocity profile.
Q9. What is the effect of the dimensionless thermal entrance on the microchannel?
This is reflected in the increase in local Nusselt number in the microchannel at a larger aspect ratio, since the relative importance of the narrow walls and corners diminishes with increasing aspect ratio.
Q10. What were the limitations of the results of the conjugate analysis?
both these sets of results were limited to a smallrange of channel aspect ratios ( = 1 to 4), and were also restricted by the available computationalresources of the time.
Q11. What can be done to simplify the conjugate analysis?
the results of such analyses can be generalized to microchannels of different dimensions, de-coupled from details of the substrate.
Q12. What are the main characteristics of the proposed correlations?
The proposed correlations are easy to use, provide detailed heat transfer coefficient predictions in the entrance region of microchannels, and cover a wide parameter range.