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I know heat travel from hot to cold places and natural airflow (e.g. wind) travel from high pressure to low pressure. But, if a forced airflow is blowing toward a hotter place, would the heat travel upstream and warm up the source of the airflow?

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Heat can be transported by heat conduction, convection and heat radiation. Heat can definitely be transferred by heat radiation against an air stream.

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Yes, This phenomena is apparent in forest fires, in which the fire travels DOWN the hill against the updraft. The reason is that thermal radiation goes up as the 4th power of absolute temperature, so thermal radiation dominates at high temperatures as seen in fires. (Stefan-Boltzmann law.)

At room temperature, convection and radiation are about equal. But if the temperature of the radiant object is, say, 1200C (1500 K), that's 5X the 300K room temperature. So 5 x 5 x 5 x 5, or the thermal transfer by radiation is now 625 times stronger! This can explain the rapid advance of forest fires as well as the ability of fires to flash ignite entire buildings rapidly.

Your question seems to be asking an engineering question about a particular geometry. More details would be needed for that specificity.

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If you are talking about (a) heat conduction and (b) heat convection by fluid flow in the opposite direction, then this can definitely be modeled to help answer your question. Consider heat conduction in the positive x-direction combined with fluid flow in the negative x-direction with speed V. Let's focus on the region from $x = 0$ to $x =\infty$, and let the temperature at x = 0 be maintained at $T_1$, while the temperature at large x is equal to $T_0$. The heat transport equation for this situation with combined conduction and convection is described by: $$-\rho CV \frac{dT}{dx}=k\frac{d^2T}{dx^2}$$where the left hand side represents the convection back toward x = 0, and the right hand side represents conduction. $\rho$ is the fluid density, C is the fluid heat capacity, and k is the fluid thermal conductivity. The solution to this equation, subject to the prescribed boundary conditions is given by: $$T=(T_1-T_0)e^{-\frac{Vx}{\alpha}}+T_0\tag{1}$$where $\alpha$ is the thermal diffusivity: $$\alpha=\frac{k}{\rho C}$$According to Eqn. 1, the length scale for the temperature variation near x = 0 is on the order $\alpha/V$. The thermal diffusivity of water at room temperature is $0.143 \times 10^{-6}\ \frac{m^2}{s}$, so even for a small fluid velocity of 0.1 m/s, the temperature disturbance at x = 0 would only propagate upstream a few microns in x. Even for air, which has a thermal diffusivity at room temperature and 1 atm a little over 100 times that of water, the disturbance would still only propagate upstream on the order of a few tenths of a millimeter.

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