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An analogy: you have a maze you're going to push marbles through. There is carpeting, so there is substantial resistance to the marbles moving (to emulate restrictive passageways of heat sink channels and radiator tubes). You push a marble into the maze, but it stops not too long after it enters. You push a second one in and it pushes the first one a little bit further, but they both then stop. You continue to do this and get the marbles pushing through the system up to a reservoir. At that point, if there are still other pathways the marbles need to go before getting to where you can take them to push them back into the loop, the marble will need to go into the reservoir and completely/mostly fill the reservoir before the will start pushing marbles through the subsequent pathways. If the reservoir is at the end, where you able to pick them to push back into the loop, then there is no need to fill up the reservoir for the loop to function, and the reservoir allows for different levels of marbles without affecting the ability to pick another marble that has gone through the loop to be put back in.For a water loop with a reservoir immediately before the pump, the fluid has gone through all of the components in the system and is then dumped in the cylinder. The motivating force drawing the fluid into the pump in the negative pressure created by the pump and gravity (not much from gravity other than keeping the liquid toward the side of the pump intake) and can compensate for different fluid levels and allow the pump to always draw a constant amount of fluid (assuming no vortex or aeration issues). If you have the reservoir in the middle of the loop, then it will need to fill it up to maintain the pressure across it to continue the pressure through the subsequent components in the loop.Adding additional water to the system increases the thermal capacity of the water. You need to think about it in units of energy. 1 calorie will raise the temperature of 1 gram of water by 1 degreeC. 1 calorie will only raise the temperature of 2 grams of water by 1/2 degreeC.
An analogy: you have a maze you're going to push marbles through. There is carpeting, so there is substantial resistance to the marbles moving (to emulate restrictive passageways of heat sink channels and radiator tubes). You push a marble into the maze, but it stops not too long after it enters. You push a second one in and it pushes the first one a little bit further, but they both then stop. You continue to do this and get the marbles pushing through the system up to a reservoir. At that point, if there are still other pathways the marbles need to go before getting to where you can take them to push them back into the loop, the marble will need to go into the reservoir and completely/mostly fill the reservoir before the will start pushing marbles through the subsequent pathways. If the reservoir is at the end, where you able to pick them to push back into the loop, then there is no need to fill up the reservoir for the loop to function, and the reservoir allows for different levels of marbles without affecting the ability to pick another marble that has gone through the loop to be put back in.
For a water loop with a reservoir immediately before the pump, the fluid has gone through all of the components in the system and is then dumped in the cylinder. The motivating force drawing the fluid into the pump in the negative pressure created by the pump and gravity (not much from gravity other than keeping the liquid toward the side of the pump intake) and can compensate for different fluid levels and allow the pump to always draw a constant amount of fluid (assuming no vortex or aeration issues). If you have the reservoir in the middle of the loop, then it will need to fill it up to maintain the pressure across it to continue the pressure through the subsequent components in the loop.
Adding additional water to the system increases the thermal capacity of the water. You need to think about it in units of energy. 1 calorie will raise the temperature of 1 gram of water by 1 degreeC. 1 calorie will only raise the temperature of 2 grams of water by 1/2 degreeC.
