Hochschule Karlsruhe Hochschule Karlsruhe - University of Applied Sciences
Hochschule Karlsruhe Hochschule Karlsruhe - University of Applied Sciences
Kälte-, Klima- und Wärmepumpentechnologie

Refrigeration, air conditioning and heat pump technology - Projects


Sustainable Off-grid solutions for Pharmacies and Hospitals in Africa

The EU project “SophiA”, which started in October, aims at developing two solar-powered 40-foot container systems for remote hospitals in Africa. A first container will provide reliable cooling and storage of vaccinations, medicines and blood plasma at low cost. The cooling requirement at three different temperature levels (+5, -30 and -70 ° C) is reached efficiently and with climate-friendly natural refrigerants. In addition to the refrigerated container, a second container ensures a secure power supply and supplies the hospital with clean drinking water and hot water as well as steam for sterilization.


Snow cabin

As a gentler alternative to cool down after a hot sauna session, the use of a snow cabin comes into consideration. Here one goes into a cold room, in which artificial snow is. Through the snow, the body can be cooled more gently.
Snow cabins are a special custom in the world of saunas and you will not find them in all saunas.

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Refrigeration systems with propane (R290)

In the course of the Ecodesign Directive, increasingly stringent requirements are being placed on liquid chillers with regard to minimum energy efficiency values. In some areas of application, the minimum efficiency values can only be achieved at great expense with conventional systems using conventional partially halogenated hydrocarbons as refrigerants. One way to improve the energy efficiency of such systems is to use propane as a refrigerant. In comparison, propane has good thermodynamic properties and a low climate impact (GWP = 3).

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Bohrlöchern mit Tiefen bis zu 2000 Metern in Aydin (Türkei)
Steam Booster Cooling System

As part of a research project ProSolarDSKM, a demonstration plant for solar thermal process steam and chilled water generation with evacuated tube collectors, steam jet chiller and latent heat storage was set up at Karlsruhe University of Applied Sciences and its operating behavior was investigated. The motivation of the project was to develop technologies to increase efficiency and sustainability for industry and production. The system was used to research the aforementioned technologies and is operated as a solar building cooling system at Karlsruhe University of Applied Sciences.

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Completed projects

Ice Slurry

DBU Project Recrystallisation

In 2017, the possibility of improving the energy efficiency and operational stability of environmentally friendly icebreaking plants by using recrystallization-inhibiting substances was investigated jointly with the Institute of Bio- and Food Technology (LVT) of the Karlsruhe Institute of Technology (KIT). In addition to the energy efficiency of the plant, the background of the project was the dissemination of the recrystallization-inhibiting technology.

Project Innovative Projects Hypothermia

Already in 2016, IKKU researched the generation of ice slurry using the supercooling method as part of an IAF project. In this method, the ice slurry fluid is cooled to below freezing temperature in a heat exchanger and then excited to phase change in a downstream crystallization unit. Initial research on the topic included the influence of different parameters, such as the subcooling temperature, the cooling rate, or the surface roughness, on the reproducible subcooling capability of an icebreifluid. 

ZIM Project Schlegel

As part of the ZIM project Schlegel in 2013, IKKU conducted research on an ice pulp heat pump with a focus on the energy efficiency of the system. In addition to the use of propane as a refrigerant, the special features of the project lay in the ice-purge generation technology. The rinsing method was investigated as a new process, in which ice freezes on evaporator tubes and the ice is then removed again with pressure.

Project ice ice sensor

One of the development goals of the ZIM project Icebreak Sensor in 2011 was to implement a sensor system that provided information on the density, sound velocity and flow rate of icebreak. The information was used to determine both the icebreak concentration and the concentration of the freezing point lowering additive.

Projekt Nock

In the cooperative project with Nock, the general suitability of ice slurry as a refrigerant for cooling components on food processing machines was determined in 2011. The main focus was on the functional and pumpability of ice slurry at temperatures of -20 °C and specified pipe cross sections.

Projekt Eckert Rührer

As part of the ZIM project Eckert Rührer in 2013 IKKU researched the development of an icebreaker with a new type of agitator. Unlike most conventional suspensions, where solids with higher density are swirled up in a liquid phase, the requirement for the stirring element of an icebreak reservoir is to "swirl off" the ice, since the ice has a lower density than the liquid solution. In addition to the optimal distribution of the ice slurry, another goal was to reduce the energy input by the adapted agitator.

Energy efficiency

Project Inductive Ice Detachment / Crystal Detachment

In two ZIM research projects (2015 & 2019), an approach of a new detachment of ice during the formation of an ice-water suspension was tested. Previously, ice particles were frozen out from a liquid on a heat exchanger surface and then sheared off from the heat exchanger surface with a scraper. However, the scratch evaporation method has many disadvantages, such as mechanical wear or high base power consumption. The new approach was based on detaching the ice by briefly melting it on the heat exchanger surface via an inductive heat pulse.

Project Eckert - Flooded evaporator

The goal of this 2017 Eckert ZIM project was to increase the energy efficiency of a compression refrigeration system using a new evaporator technology. The new technology combined the dry expansion method with the flooded evaporator method by shifting the superheat completely to an internal heat exchanger.

Project Eckert Latent Cold Storage

The goal of this further ZIM project Eckert in 2017 was to develop a latent cooling system that made it possible to avoid inefficient partial load operation of a refrigeration plant. The latent heat storage system offers the opportunity to keep the refrigeration process at a constant and designed nominal capacity while increasing the plant efficiency. Another project task was to develop an intelligent control system that would help the storage concept found to optimally adjust to the operating state of an already existing refrigeration plant.

Project Nitrous Oxide - Follow-up Project to Project Christ

Based on the results of the investigations into the replacement of synthetic refrigerants in freeze-drying processes with natural, non-flammable refrigerants, another ZIM project followed in 2016. In this N2O project, a test bed was set up to confirm the suitability of an N2O-CO2 mixture as a low-temperature refrigerant down to -50 °C. The results of this test were used to develop a new refrigerant.

Project Christ

As early as 2013, the ZIM project Christ investigated the fundamental possibility of replacing synthetic refrigerants in freeze-drying processes with natural and non-flammable refrigerants. The reason for this project was the fact that so far only refrigerants with a high greenhouse potential could be used for freeze-drying processes.

Project Samsung

In 2013, IKKU investigated possible processes for efficient drying of dishes after the washing process in a dishwasher using the heat pump principle in the Samsung project.  

Project Stierlen

In the Bulling 2012 research project, IKKU investigated the cooling behavior of various insulated food service systems with special heat-retaining inserts (so-called pellets). The focus was on the cooling behavior of hot food in the insulated ware systems under conditions that were as real as possible. Consequently, the findings were applied to a theoretical model with which it is possible to determine the optimum ratio of insulating foam thickness to food mass in terms of cooling behavior.

Natural refrigerants

Follow-up industrial project with Bitzer and Fuchs

The successful results led to an additional industry-funded project in which the built-up test carrier with the N2O-CO2 mixture was further investigated. The investigations dealt with safety aspects regarding the refrigerant as well as long-term tests, with simultaneous expansion of the test conditions.

Solar cooling

Process steam and cooling generation with solar collectors, steam jet chiller and latent heat storage systems

Together with the Frauenhofer Institute, a demonstration plant for solar thermal process steam and chilled water generation with evacuated tube collectors, steam jet chiller and latent heat storage was set up at Karlsruhe University of Applied Sciences and its operating behavior was investigated. With the demonstration plant, direct steam generation with evacuated tube collectors and the steam jet chiller as an open process in combination with a latent heat and latent cold storage system were implemented for the first time. The plant is used to research the technologies mentioned and is operated as a solar building cooling system at Karlsruhe University of Applied Sciences.