The Woodruff School

SUMMARY

The vapor-absorption cycle is a promising technology for thermally driven cooling and heating applications. While this cycle has been known for over a century, it has found applications in only very specific and large capacity installations. With the development of advanced concepts for miniaturized heat and mass exchangers, this technology can now be implemented in small-scale applications for waste-heat recovery or thermally driven cooling and heating. These small-scale systems operate under varying conditions of load and ambient temperature. This necessitates a well-designed control system to maintain optimal performance of these heat pumps. Design of control system requires a transient model of the system to predict the response to changes in operating conditions and tunable inputs. Traditionally, the transient models for heat pump systems have been developed using detailed segmented models. These models are computationally expensive and unsuitable for control system design. The first part of the research effort outlined here will focus on the development of reduced-order models to predict the transient behavior of absorption systems. These models will utilize concepts such as moving-boundary lumped models and reduced-order modeling of the desorber component using techniques typically employed in the modeling of distillation columns. The computational advantage and suitability for control system design of these models will be highlighted. Following model development, control strategies based on these models will be designed and evaluated. The control techniques will be based on feedback of key variables, such as evaporator temperature glide, desorption temperature, ambient conditions, and cooling load requirement. These efforts will culminate in experimental evaluation of first generation control strategies on a 3.5 kW cooling capacity ammonia-water absorption system. The validation of dynamic models will be followed by analysis of advanced control algorithms, such as advanced feedback control methods and multiple-input multiple-output feedback control.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Anurag Goyal

TIME:	Thursday, July 20, 2017, 10:00 a.m.

PLACE:	MRDC Building, 4211

TITLE:	Dynamics and Control of Ammonia-water Absorption Heat Pumps

COMMITTEE:	Dr. Srinivas Garimella, Chair (ME) Dr. Sheldon M. Jeter (ME) Dr. Satish Kumar (ME) Dr. Thomas F. Fuller (ChBE) Dr. James E. Braun (ME, Purdue University)

SUMMARY The vapor-absorption cycle is a promising technology for thermally driven cooling and heating applications. While this cycle has been known for over a century, it has found applications in only very specific and large capacity installations. With the development of advanced concepts for miniaturized heat and mass exchangers, this technology can now be implemented in small-scale applications for waste-heat recovery or thermally driven cooling and heating. These small-scale systems operate under varying conditions of load and ambient temperature. This necessitates a well-designed control system to maintain optimal performance of these heat pumps. Design of control system requires a transient model of the system to predict the response to changes in operating conditions and tunable inputs. Traditionally, the transient models for heat pump systems have been developed using detailed segmented models. These models are computationally expensive and unsuitable for control system design. The first part of the research effort outlined here will focus on the development of reduced-order models to predict the transient behavior of absorption systems. These models will utilize concepts such as moving-boundary lumped models and reduced-order modeling of the desorber component using techniques typically employed in the modeling of distillation columns. The computational advantage and suitability for control system design of these models will be highlighted. Following model development, control strategies based on these models will be designed and evaluated. The control techniques will be based on feedback of key variables, such as evaporator temperature glide, desorption temperature, ambient conditions, and cooling load requirement. These efforts will culminate in experimental evaluation of first generation control strategies on a 3.5 kW cooling capacity ammonia-water absorption system. The validation of dynamic models will be followed by analysis of advanced control algorithms, such as advanced feedback control methods and multiple-input multiple-output feedback control.