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Design of a direct-contact thermal energy storage heat exchanger for the NIST net-zero residential test facility: Part 2 Heat exchanger design.

Number: 2122

Author(s) : KEDZIERSKI M., LIN L.

Summary

This paper describes the second part of the design of a direct-contact heat exchanger (DCHEX) to be used for thermal energy storage in the Net-Zero Energy Residential Test Facility (NZERTF) at the National Institute of Standards and Technology (NIST). The heat exchanger was designed for heat exchange between a phase-change material (PCM) and refrigerant. The selection of a PCM that would be immiscible with the refrigerant and have a freezing point temperature of approximately of 285 K is covered in the Part 1 companion paper. Part 2 of the project presented here provides a design for direct-contact heat exchange between octanoic acid (continuous phase) and the dispersed phase R410A. Twin DCHEXs were designed to house a vertical column of PCM and to distribute the refrigerant flow throughout the PCM. The height of the PCM column was determined with measurements from the literature that were re-correlated to predict the droplet heat transfer coefficient and the required height of the PCM column. A disengagement section was designed to prevent entrainment of PCM droplets into the exiting refrigerant vapor during the PCM charging. Basic equations are provided so that the design may be modified for a different PCM mass, refrigerant flow rate, temperature difference and operating fluids. A schematic drawing of the DCHEX with placement of orifice holes, mist eliminator, and piping was given. The energy storage capacity of the DCHEX is approximately 191 MJ and has the potential of providing a 33 % energy savings in cooling the NZERTF.

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  • Original title: Design of a direct-contact thermal energy storage heat exchanger for the NIST net-zero residential test facility: Part 2 Heat exchanger design.
  • Record ID : 30030475
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2022/07/10

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