DOE/BTO/ORNL Contributions to Annex 53
Expansion Loss Reduction Using a Pressure
Exchanger
Brian Fricke

Oak Ridge National Laboratory

ORNL is managed by UT-Battelle, LLC for the US Department of Energy

Expansion Loss Reduction Using a Pressure Exchanger

Oak Ridge National Laboratory
Brian A. Fricke (R&D Staff)
865.576.0822, frickeba@ornl.gov

2Introduction – Motivation• Pressure losses are unavoidable in HVAC&R systems– Pressure drop in piping, heat exchangers, expansion devices, etc.
• Pressure loss in certain components can be recovered, e.g.,

expansion processes– Ejectors– Turbines/expanders• Transcritical CO2 refrigeration systems– Systems operate at high pressures– Expansion processes lead to significant “lost work”– System performance could be enhanced with work recovery

3Introduction – Pressure Exchanger• Design and implement “pressureexchanger” (PX) technology inrefrigeration systems• Challenges for integration– Seals are critical path component forsuccessful implementation– Laboratory data is sparse (performance withtwo-phase flow?)– Information is lacking on component designand implementation
4

Introduction – Potential Implementation• 4-Port PX for CO2 refrigeration– PX is used to replace high-pressure expansion valve and increase pressure of

the medium-temperature suction– Reduces power consumption of medium-temperature compressor– COP increases upwards of 15% if suction flow boosted by PX– Other configurations possible

5Characterization of PX• Analogy to Heat Exchangers
Heat Exchanger

6Pressure Exchanger

Transfer heat energy

Transfer work energy

Involves heat losses

Involves pressure losses

Fluids can be in liquid/gas or 2phase state

Fluids can be in liquid/gas or 2phase statePhase change process can occurduring the transport process

Phase change process can occur
during the transport process

Geometry establishes theeffectiveness

Geometry establishes theeffectivenessCharacterization of PX• Analogy to Heat Exchangers
Heat Exchanger

Pressure Exchanger

𝑞𝑚𝑎𝑥 = 𝐶𝑚𝑖𝑛 𝑇ℎ,𝑖 − 𝑇𝑐,𝑖𝑊𝑚𝑎𝑥 = 𝑣𝑚𝑖𝑛 𝑃ℎ,𝑖 − 𝑃𝑙,𝑖𝜀=𝜀=𝑞𝑞𝑚𝑎𝑥

𝐶𝑐 𝑇𝑐,𝑜 − 𝑇𝑐,𝑖𝐶𝑚𝑖𝑛 𝑇ℎ,𝑖 − 𝑇𝑐,𝑖𝜀=𝑊
𝑊𝑚𝑎𝑥

𝑣𝑙 𝑃𝑙,𝑜 − 𝑃𝑙,𝑖𝑣𝑚𝑖𝑛 𝑃ℎ,𝑖 − 𝑃𝑙,𝑖𝑞 = 𝜀𝐶𝑚𝑖𝑛 𝑇ℎ,𝑖 − 𝑇𝑐,𝑖𝑊 = 𝜀𝑣𝑚𝑖𝑛 Pℎ,𝑖 − 𝑃𝑙,𝑖𝐶𝑚𝑖𝑛
𝜀 = 𝑓 𝑁𝑇𝑈,𝐶𝑚𝑎𝑥𝑣𝑚𝑖𝑛𝑣𝑚𝑎𝑥𝑥
𝑁𝑇𝑈 ≡𝑣𝑚𝑖𝑛 ∙ ∆𝑃𝑚𝑖𝑛

𝑁𝑇𝑈 ≡7𝜀=𝑈𝐴𝐶𝑚𝑖𝑛

𝜀 = 𝑓 𝑁𝑇𝑈,

Numerical Analysis• Performance of PX modeled withcomputational fluid dynamics (CFD) software
package• Model assumptions:– Stationary inlet/outlet ports– Rotor (1,000 RPM)
– 12 channels in rotor– Channel length = 0.19 m– Channel diameter = 0.02 m– Rotor outside diameter = 0.18 m– Stationary port depth = 0.05 m
8

Numerical Analysis• Comparison of CFD model with

9existing experimental data(desalination data)

travelling distance of any flow inside
the rotor duct
– Mixing is the term that quantifies theamount of mixing that occurs
between the primary and secondary
flow inside the PX

Experimental (Xu et al.)
Numerical

76Mixing%– Inflow length is defined as the total

8543
2
10,35 0,4 0,45 0,5 0,55 0,6 0,65 0,7 0,75 0,8 0,85 0,9 0,95
Inflow Length (L)Enle Xu, Yue Wang, Liming Wu, Shichang Xu, Yuxin Wang, and Shichang Wang,“Computational Fluid Dynamics Simulation of Brine−Seawater Mixing in a Rotary
Energy Recovery Device,” Ind. Eng. Chem. Res., 53, 18304−18310, 2014.

91

Future Work• Develop a pressure exchanger test apparatus and prototype

pressure exchanger for R744 applications– Working with commercial partner to develop prototype PX• Experimental evaluation of pressure exchanger performanceusing R744

• Retrofit pressure exchanger in R744 refrigeration system

10Thank you!
Questions/Comments?

11