nice description mapesMy advice is to link irreversibility in your mind not with "energy dissipation" but with "flow in response to a gradient that tends to erase that gradient." There are a couple advantages. First, gradient-induced flow is easy to quantify, by taking the dot product of the flow vector (in this case, heat flow and direction) with the mathematical gradient of the potential (in this case, the temperature). This dot product is actually proportional to the rate of entropy increase. Second, as you've pointed out, it's not easy to visualize "energy dissipation" when a hot object heats a cold object. It's an amorphous term (how is energy dissipated here?). But the gradient-induced flow view encompasses both friction (matter deforms in response to stress gradients, energy moves in response to temperature gradients) and simple heating/cooling. Swapping these descriptions in my mind was a key part of moving from beginner to advanced thermo.