Dynamic study of local integration of high temperature heat pumps (HTHPs) in a food processing line

Abstract

This thesis conducts a dynamic integration of high temperature heat pumps (HTHPs) in a food
processing line, based on the thermodynamic efficiency and coefficient of performance. The main
goals are to decrease the energy consumption in the industry and further the operational costs, and
thereby increase the energy efficiency in the unit processing line.
The objective of this thesis is to assess the potential of HTHPs for food industrial energy recovery
by evaluating the thermodynamic principles governing heat pumps. The modeling integration is
performed, using the objective oriented language Modelica and implemented in Dymola. In order
to simulate a model inside an industrial alpha configuration double acting Stirling cycle based high
temperature heat pump.
The case study of simulation and integration were based on dairy processing line, specifically in
raw milk. The two units processing lines were pasteurization and sterilization (UHT) based on the
provided data by Tetra Pak. The range of temperatures were different for each case, from 40 °C to
90 °C for pasteurization and 65 °C to 160 °C for sterilization (UHT). The lower temperature was
the cold inlet source and the higher temperature was the hot sink for both cases.
The results shown that the heat pump had variations of power consumption and heating flow as the
crankshaft radius and frequency piston were varied in the simulations. Higher piston frequencies
and greater crankshaft radius lead to increased power consumption, especially under higher heating
flow conditions, for both cooling and heating operations. The coefficient or performance (COP)
was measured using two equations, calculating the COPcarnot based on the difference of
temperatures and COPh based on the power consumption and heating flow.
For each case of study both COP were estimated and the results showed that for pasteurization the
COPcarnot presents higher values than for UHT due to the high temperature difference for the
sterilization case. The COPh remains the same for both cases since the rate between the power
consumption and useful heating flow increase or decrease at the same time for full capacity
operation of the heat pump

Popular Abstract

This thesis conducts a dynamic integration of high temperature heat pumps (HTHPs) in a
food processing line.
In 2023, global CO₂ emissions from total energy use rose by 1.1%, with greenhouse gas
emissions hitting a record 37.4 gigatons. Among industrial sectors, the food processing
industry is a major energy consumer, heavily dependent on thermal energy for key processes
such as pasteurization and sterilization. HTHPs have emerged as a promising solution for
enhancing energy efficiency by enabling energy recovery and reuse.
This research aims to evaluate the potential of high temperature heat pumps (HTHPs) for
energy recovery in the food industry by analyzing the performance behavior of heat pumps.
Heat pumps can contribute the food industry use less energy and produce fewer carbon
emissions. The food industry consumes a lot of heat for everyday tasks like pasteurizing and
sterilizing milk, which currently rely heavily on burning fossil fuels. Unlike conventional
industrial heating systems as petrol or natural gas boilers, heat pumps can effectively replace
them to make the systems more sustainable.
To understand how efficient HTHPs can be incorporated in a food processing line, this study
performed a computer simulation to test how they work. Thinking of these heat pumps as a
thermodynamic approach in advanced machines that move heat from one side to another side
simulating a fridge or air-conditioned system. The goal was to see how well they could
recover and reuse waste heat during raw milk processing, which uses a lot of energy, specially
coming from burning fossil fuels. The research focused on two common dairy tasks, with
data given by the company Tetra Pak AB as a study case. Pasteurization (process to heat the
milk and eliminate microorganism) and sterilization or ultra-high temperature (UHT), that is
the same process of pasteurization but using higher temperatures a for a longer shelf life. The
model tested how the heat pump performed under different temperatures, ranging from 45°C
to 90°C for pasteurization and from 65°C to 165°C for sterilization.
The study found that some operational and design parameters of the heat pump, as the piston
frequency or the radius of the engine shaft, can influence on the power consumption and total
performance of the machine. These parameters can make the consumption either higher or
lower depending on the variation. The efficiency of the heat pump was analyzed measuring
the performance using two ways: one looking at how the system worked based on
temperatures differences, and the other compared the heat output to the energy consumed. It
turned out that the heat pump was more efficient in pasteurization because of the lower
temperature gap. But it general, the system remained steady and balanced in the energy
consumption for both scenarios running at full capacity.

• author: Castellanos Ayala, Gabriel Fernando
• supervisor: Hamid Ghanbari; Xin Bin; Martin Andersson
• organization: Department of Energy Sciences
• course: MVKM05 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: heat pumps, temperature, coefficient of performance, power consumption, piston frequency, crankshaft radius, heat flow, heating, cooling, source, sink, pasteurization, sterilization.
• report number: ISRN: LUTMDN/TMPH-25/ 5635-SE
• ISSN: 0282-1990
• language: English
• id: 9199431
• date added to LUP: 2025-06-16 11:29:57
• date last changed: 2025-06-16 11:29:57