摘要
某大科学装置恒温空调冷冻水系统需配备超高精密级(即温度波动≤±0.1 ℃)且抗干扰能力强的冷冻水系统.传统电加热调节无法解决冷冻水温度高频振荡的问题.通过缩尺实验,验证了板式换热器和混水泵两种方案用于提供超高精密级冷冻水的可行性;建立了基于两种方案的Modelica仿真模型并进行实验验证;基于Modelica模型仿真,量化并对比了两种方案下冷冻水温度控制的稳态和动态性能.结果表明:两种方案均可在一定硬件水平下实现±0.1℃内温度波动控制,板换方案稳态性能较优,两种方案下全时段内的RMSE(均方根误差)均低于0.1 ℃;板式换热器和混水方案的调节时间分别为5 000 s和600 s,混水泵方案动态性能较优;板式换热器和混水方案均可对冷冻水供水温度高频振荡进行"主动削峰",削峰系数分别为0.07和0.4.
Abstract
A large-scale scientific facility uses constant-temperature air conditioning(CTAC)to control the air temperature fluctuation at an ultrahigh precision,i.e.,≤±0.1 ℃,which implies that the temperature of the chiller water must also be maintained at an ultrahigh precision level.Traditional CTACs depend on electric heating to maintain the chilled water temperature.However,such methods usually fail to address the issue of high-frequency oscillations and typically are not applied to ultrahigh-precision control.In this study,by conducting a reduced-scale experiment,we first validated the feasibility of two water chillers,one using a plate heat exchanger and another using a mixed water pump,to provide chilled water at an ultrahigh precision.Simulations using Modelica models based on these two approaches were established and experimentally verified.Finally,the steady-state and dynamic performances of these two systems were compared.Both approaches can achieve±0.1 ℃ temperature fluctuation control when the hardware meets specific criteria,with the plate heat exchanger approach exhibiting superior steady-state performance.Under both schemes the root mean square error(RMSE)for the entire time period is below 0.1 ℃.The settling times for the plate heat exchanger and mixed water pump approaches are 5 000 s and 600 s,respectively.The mixed water pump approach exhibits better dynamic performance.Both plate heat exchanger and mixed water pump approaches are capable of actively dampening high-frequency oscillations in the water supply temperature,with damping coefficients of 0.07 and 0.4,respectively.
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