Session: K6-09: HEAT TRANSFER IN ENERGY SYSTEMS - WASTE HEAT II

Paper Number: 138496

138496 - Enhancing Steam Accumulator Performance With Packed-Bed Latent Heat Storage 

Abstract: 

Intermittent demand for steam in various industrial sectors presents challenges in maintaining a consistent supply. Over-designed boilers, a common solution to this intermittency, lead to inefficiencies and increased costs. Likewise, the use of waste heat often requires coordinating supplies and loads that are mismatched in time and intensity. Steam accumulators are a useful technology to address these needs. Functioning as thermal energy storage systems, they balance steam supply and demand by storing excess heat during periods of low demand and releasing it when needed. They store energy via the sensible heat of saturated water. When pressure drops, a portion of this water flashes to steam, allowing for high instantaneous steam flow rates for brief periods, evening out peak loads.  However, the energy density of these systems is limited by the relatively small sensible heat that can be accessed. For instance, if a steam accumulator is charged at about 550 kPa-g and discharged at 350 kPa-g, only around 3% of the stored water mass turns into steam.

Augmented accumulators utilize additional thermal storage elements beyond the sensible heat of water.  This study investigates the incorporation of polymeric phase change materials (PCM) for steam generation in pressure-drop steam accumulators. This provides potential for dramatically higher energy density.  For example, the specific enthalpy of commonly available polymers may allow a 3x increase in steam production per unit volume. Here, a thermodynamic framework is established to quantify steam generation capacity under diverse operating conditions. We also present a kinetic model to quantify heat transfer and steam generation within the system. A quasi-steady approximation is utilized to focus on latent heat effects during phase change. Performance assessments are conducted under constant pressure and constant thermal energy output conditions.  Key findings reveal operational advantages of the PCM-enhanced system.  These benefits include smaller tank size, reduced costs, and enhanced safety. However, there are corresponding trade-offs. For example, the discharge rate is limited and the long-term durability of PCMs in steam accumulators is still uncertain.  We consider the benefits of augmented steam accumulators in specific application scenarios including waste heat recycling and heat pump integration.

Presenting Author: Souvik Roy University of California, Merced

Presenting Author Biography: Souvik Roy is a Ph.D. in Mechanical Engineering from the University of California, Merced, with a strong background in thermal energy storage, phase change materials, and finite element analysis. Souvik holds a Master's degree in Mechanical Engineering from Rensselaer Polytechnic Institute, where he worked on advanced simulation tools for selective laser melting additive manufacturing processes and contributed to an IBM Watson-sponsored project on finite element simulation for wafer laser grooving in chip singulation.

During his time as a graduate research assistant at UC Merced, Souvik has worked on numerous projects, including the evaluation of pilot-scale thermal energy storage units, synthesis of novel polymeric phase change materials, and the design of steam accumulators with phase change materials for enhanced steam generation.

Souvik has been recognized for his academic achievements with prestigious awards, such as the Dan David Solar Fellowship and the Fred and Mitzie Ruiz Fellowship at UC Merced. He has published peer-reviewed papers and presented his work at conferences, showcasing his expertise in thermal analysis and mechanical engineering.

Outside of his academic and professional life, Souvik is passionate about nature photography and has recently taken up bird watching with his new pair of binoculars. He also enjoys challenging his mind by playing Sudoku in his spare time.

Authors:

Souvik Roy University of California, Merced
James Palko University of California, Merced