[Asmodian]

A big enough chiller can keep your liquid temp at 20°C, or whatever you want forever (too low is hard, but down to -10°C isn't too bad). It would be expensive, use a lot of power, and output a lot of heat, but it can do it. Generally I would recommend not using radiators with a chiller unless you were targeting above ambient liquid temperatures.

I am not sure what you mean by "keep water temp at 20°C instantly"?

 

[Thanh Nguyen]

When turn on the chiller, the water is cooled down to 20c instantly.

 

[Asmodian]

When turn on the chiller, the water is cooled down to 20c instantly.

No. It will always take a bit to chill down. The bigger and more powerful the chiller the faster it can do it but it takes a lot of energy extracted to cool down water and it will need to circulate for a bit too.

It also depends on the volume of water in your loop, the smaller the volume or mass of water the faster it can cool down.

 

[StAndrew]

Yeah, it won't be immediate unless you keep your chiller running at all times. Either way, you will have to find a way to prevent condensation.

Also, without proper ambient air temp control, your chiller will be running a positive feedback loop: increasing ambient air temps which increases chiller load which increases ambient air temps more... you might even get too hot for your chiller to work properly. Either way, your computer may be chilly but you'll be soaking in sweat.

If the issue is ambient air temps, turn up the A/C or get a window/portable A/C unit. It'll be less risk to your computer (no condensation risks), about the same price, and even help you avoid extreme swamp butt after gaming for a few hours