Precision Temperature Control of High-Throughput Fluid Flows: Theoretical and Experimental Analysis

Abstract

A precision method for attenuating temperature variations in a high-throughput control fluid stream is described and analyzed. In contrast to earlier investigations, the present study emphasizes heat transfer analysis of the constituent control device and derives theoretical descriptions of system responses to time-varying fluid temperatures. Experiments demonstrate that the technique provides: (1) frequency-dependent attenuation which is several orders of magnitude greater than that obtained via a perfect mixing volume; (2) attenuation, over two decades of disturbance frequency, that reduces in-flow temperature variations by factors ranging from 10 to ≈104; (3) asymptotic attenuation greater than three orders of magnitude for spectral components having periods less than the device thermal equilibrium time; and (4) attenuation which is fully consistent with theoretical predictions. The model developed provides design criteria for tailoring system performance. In particular, it is shown that for a given control stream flow rate, the magnitude of maximal attenuation can be adjusted by varying the thermal resistance between the flow and attenuating medium, while the range of frequencies maximally attenuated can be adjusted by varying the product of thermal resistance and attenuating medium heat capacity. The analysis and design are general and should prove useful in the design and analysis of other high-throughput precision temperature control systems.