Article, 2024

Thermal design and optimization of high-temperature heat pump integrated with district heating benchmarked in Denmark for process heat supply

International Journal of Refrigeration, ISSN 1879-2081, 0140-7007, Volume 159, Pages 356-370, 10.1016/j.ijrefrig.2023.12.025

Contributors

Sadeghi, Mohsen 0000-0002-4004-1240 [1] Petersen, Tage [2] Yang, Zhenyu (Corresponding author) [1] Zühlsdorf, Benjamin 0000-0001-9911-9164 [2] Madsen, Kim Stenholdt [3]

Affiliations

  1. [1] Aalborg University
    2. [NORA names: AAU Aalborg University; University; Denmark; Europe, EU; Nordic; OECD];
  2. [2] Danish Technological Institute
    3. [NORA names: Danish Technological Institute; GTS Institutes; Denmark; Europe, EU; Nordic; OECD];
  3. [3] DIN Forsyning A/S, 6715, Esbjerg, Denmark
    4. [NORA names: Denmark; Europe, EU; Nordic; OECD]

Abstract

This work aims to assess and optimize the performance of cascade high-temperature heat pump (HTHP) integrated with district heating (DH) to produce 1 MW steam at 160 °C for the industrial processes. The heat available in the primary loop of the DH network at 80 °C is considered as the heat source; which is cooled down 70 °C through the HTHP evaporator, before supplying the DH secondary loop. The use of alternative hydrocarbons in the low-temperature loop are examined; and considering the gas compressor limitation, the HTHP performance of using each refrigerant is optimized and compared to each other. The optimization results reveal that pentane- hydrocarbon with the highest critical temperature- is the most promising refrigerant to be paired with steam in the high-temperature loop, reaching the highest COP of 2.66. However, concerning safety and compressor sizing issues, butane is an excellent candidate; with volumetric heating capacity (VHC) of about two times more than that of pentane, in the expense of just about 4 % reduction in the HTHP COP. In addition, water injection theoretically controls the steam compressor discharge temperature successfully, with just 0.9 K superheating at the compressor outlet; and reduces its power consumption and the HTHP COP up to 4.3 % and 1.7 %, respectively. Moreover, techno-economic analysis demonstrates that the HTHP technology shows a better business case compared to the conventional natural gas and electric boilers.

Keywords

COP, DH network, Denmark, alternant hydrocarbons, analysis, boiler, business, business case, butane, candidates, capacity, cases, compressor, compressor discharge temperature, compressor limits, compressor outlet, consumption, conventional natural gas, design, discharge temperature, district, district heating, electric boiler, evaporation, excellent candidate, expense, gas, heat, heat capacity, heat pump, heat source, heat supply, high temperature heat pump technology, high-temperature heat pump, high-temperature loop, higher COP, hydrocarbons, industrial processes, injection, issues, limitations, loop, low temperatures, low-temperature loop, natural gas, network, optimal results, optimization, outlet, pentane, performance, power, power consumption, primary loop, process, process heat supply, pump, reduction, refrigeration, results, safety, secondary loop, size issues, source, steam, supply, techno-economic analysis, technology, temperature, thermal design, volumetric heat capacity, water, water injection

Funders

  • Danish Energy Agency

Data Provider: Digital Science

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