Model predictive control of vapor compression cycle for large transient heat flux cooling

2016 ◽  
Author(s):  
Zehao Yang ◽  
Daniel T. Pollock ◽  
John T. Wen
Keyword(s):  
Heat Flux ◽  
Model Predictive Control ◽  
Predictive Control ◽  
Vapor Compression ◽  
Vapor Compression Cycle ◽  
Compression Cycle ◽  
Transient Heat Flux

Offset-free model predictive control of a vapor compression cycle

2012 ◽  
Vol 22 (7) ◽  
pp. 1374-1386 ◽  
Author(s):  
Matt Wallace ◽  
Buddhadeva Das ◽  
Prashant Mhaskar ◽  
John House ◽  
Tim Salsbury
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Vapor Compression ◽  
Vapor Compression Cycle ◽  
Compression Cycle ◽  
Free Model

A Model Predictive Control Law for a Vapor Compression Cycle System

2016 ◽  
Author(s):  
Anhtuan D. Ngo ◽  
Joshua R. Cory
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Thermal Load ◽  
Cooling System ◽  
Thermal System ◽  
Control Input ◽  
Vapor Compression ◽  
Error Performance ◽  
Vapor Compression Cycle ◽  
Compression Cycle

During the development of next generation tactical aircraft, thermal management is given significant consideration due to higher transient cooling demands, with stricter temperature limits along with the smaller size and weight in the cooling system hardware. Traditional control approaches, such as proportional-integral-derivative (PID), are sufficient to achieve the desired steady-state error performance for a thermal system with no constraints on the control inputs. The traditional control techniques may not be well-suited for thermal systems with constrained inputs. In this paper, we apply the Model Predictive Control (MPC) technique on an input-constrained thermal system and examine the system performance under a large transient thermal load and control input limits through the anticipation of the known thermal load. The results include design and implementation of an MPC controller for a high-fidelity, nonlinear vapor compression cycle model, as well as comparison of the MPC results to those of a finely tuned PID controller.

The Steady-State Modeling and Analysis of a Two-Loop Cooling System for High Heat Flux Removal

2009 ◽  
Author(s):  
Rongliang Zhou ◽  
Juan Catano ◽  
Tiejun Zhang ◽  
John T. Wen ◽  
Greg J. Michna ◽  
...  
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Heat Exchangers ◽  
Cooling System ◽  
High Heat ◽  
System Structure ◽  
High Heat Flux ◽  
Vapor Compression ◽  
Vapor Compression Cycle ◽  
Compression Cycle

Steady-state modeling and analysis of a two-loop cooling system for high heat flux removal applications are studied. The system structure proposed consists of a primary pumped loop and a vapor compression cycle (VCC) as the secondary loop to which the pumped loop rejects heat. The pumped loop consists of evaporator, condenser, pump, and bladder liquid accumulator. The pumped loop evaporator has direct contact with the heat generating device and CHF must be higher than the imposed heat fluxes to prevent device burnout. The bladder liquid accumulator adjusts the pumped loop pressure level and, hence, the subcooling of the refrigerant to avoid pump cavitation and to achieve high critical heat flux (CHF) in the pumped loop evaporator. The vapor compression cycle of the two-loop cooling system consists of evaporator, liquid accumulator, compressor, condenser and electronic expansion valve. It is coupled with the pumped loop through a fluid-to-fluid heat exchanger that serves as both the vapor compression cycle evaporator and the pumped loop condenser. The liquid accumulator of the vapor compression cycle regulates the cycle active refrigerant charge and provides saturated vapor to the compressor at steady state. The heat exchangers are modeled with the mass, momentum, and energy balance equations. Due to the projected incorporation of microchannels in the pumped loop to enhance the heat transfer in heat sinks, the momentum equation, rarely seen in previous refrigeration system modeling efforts, is included to capture the expected significant microchannel pressure drop witnessed in previous experimental investigations. Electronic expansion valve, compressor, pump, and liquid accumulators are modeled as static components due to their much faster dynamics compared with heat exchangers. The steady-state model can be used for static system design that includes determining the total refrigerant charge in the vapor compression cycle and the pumped loop to accommodate the varying heat load, sizing of various components, and parametric studies to optimize the operating conditions for a given heat load. The effect of pumped loop pressure level, heat exchangers geometries, pumped loop refrigerant selection, and placement of the pump (upstream or downstream of the evaporator) are studied. The two-loop cooling system structure shows both improved coefficient of performance (COP) and CHF overthe single loop vapor compression cycle investigated earlier by authors for high heat flux removal.

Multivariable Control of Vapor Compression Cycle With Transient Heat Flux

2013 ◽  
Author(s):  
Zehao Yang ◽  
Daniel T. Pollock ◽  
John T. Wen
Keyword(s):  
Heat Flux ◽  
Open Loop ◽  
Controller Synthesis ◽  
Operating Point ◽  
High Heat Flux ◽  
Vapor Compression ◽  
Worst Case ◽  
Vapor Compression Cycle ◽  
Compression Cycle ◽  
Model Linearization

This paper investigates feedback control of refrigeration cycles for high heat-flux cooling applications, where large transient heat loads may be present. We apply H∞ controller synthesis for disturbance rejection, with the evaporator heat-flux treated as the disturbance input. The controller synthesis is based on model linearization about a chosen operating point. We analyze model uncertainty due to the linearization error to ensure robustness of the closed-loop systems. We use a low-order, lumped-element nonlinear model for the vapor compression cycle. We obtain linearized systems at different operating points, and quantify system nonlinearity using the H∞ norm. Controllers synthesized for the chosen nominal systems are tested for both nominal (near the operating point) and the worst-case performance in nonlinear simulations. For systems close to critical heat-flux (CHF), it is shown that a trade-off exists between the nominal performance and robust stability. For systems far away from CHF, it is shown that the open-loop system has the optimal cooling capacity. The performance of H∞ controller for systems near CHF is validated by experiment.

Experimental Model Identification and Controller Design of a Vapor Compression Cycle for Electronics Cooling

2010 ◽  
Author(s):  
Juan E. Catano ◽  
Tiejun Zhang ◽  
Rongliang Zhou ◽  
Michael K. Jensen ◽  
Yoav Peles ◽  
...  
Keyword(s):  
Heat Flux ◽  
Model Identification ◽  
Electronics Cooling ◽  
Heating Element ◽  
Vapor Compression ◽  
Dynamic Identification ◽  
Flux Boundary Condition ◽  
Highly Nonlinear ◽  
Vapor Compression Cycle ◽  
Compression Cycle

In this paper dynamic identification of the evaporator dynamics in a vapor compression cycle (VCC) subjected to imposed heat flux is studied. The imposed heat flux boundary condition at the evaporator represents a specific application of the VCC for electronics cooling. However, different models and control algorithms than traditional VCCs are required. First principle models are highly nonlinear and, hence, not practical for system control. A dynamic model identification of the refrigerant temperature at the exit of the evaporator, refrigerant pressure, and temperature of the heating element is performed by varying the expansion valve opening. It is shown that single-input single-output (SISO) identification is not sufficient to capture the dynamics of the evaporator, due to the coupling of the dynamics in the entire system. Including the effect of incoming mass flow rate into the evaporator to the model significantly improves the identification and prediction of the evaporator dynamics. Finally, a SISO controller based on the identified model, is designed and tested experimentally. The control objective is to maintain the temperature of the heating element below a set point, subjected to changes in heat flux.

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