About Industrial Refrigeration

Industrial refrigeration is a specialized field that deals with cooling and freezing large-scale industrial processes and equipment. It is essential in food and beverage, pharmaceuticals, and chemical manufacturing industries, where temperature control is critical to maintaining product quality and safety

Industrial refrigeration systems are much larger and more complex than typical residential or commercial refrigeration systems, with components such as compressors, condensers, evaporators, and control systems designed to handle heavy-duty cooling loads.

The refrigerants used in industrial refrigeration systems often differ from those used in residential and commercial systems, as they must operate at much lower temperatures and handle higher pressures. Proper maintenance and servicing of industrial refrigeration systems are essential to ensure optimal performance and prevent costly downtime and product loss.

What is The Difference Between Commercial And Industrial Refrigerators?

Commercial refrigerators are typically smaller and used in restaurants, grocery stores, and convenience stores. These containers are intended for holding small amounts of food and beverages and are frequently utilized for presentation. Even though they are durable and can withstand continuous use, they are not suited for heavy-duty industrial use.

On the other hand, industrial refrigerators are much larger and designed for heavy-duty use in industries such as pharmaceuticals, chemical processing, and food production. They're typically used to store large quantities of temperature-sensitive products and are built to withstand harsh industrial environments. Industrial refrigerators often have more advanced temperature control systems and can maintain precise temperature ranges.

Key Components

An industrial refrigeration system has five core components: refrigerant, compressor, condenser, metering device, and evaporator. Below is a description of them:

Compressor

When refrigerant undergoes vaporization due to heat, it enters the compressor, a device that elevates the pressure and temperature of the vapor. For the refrigeration cycle to continue, the temperature must exceed the condensing fluid. The compressor functions as a pump to maintain refrigerant flow within the system.

An industrial compressor may belong to one of the following categories.

• Screw
• Piston
• Centrifugal
• Rotary
• Condenser

A condenser, or a coil, is where refrigerant goes after leaving the compressor. Generally, the condenser coil is exposed to something cool, which allows the refrigerant to release heat. The fluids can range from outdoor air to water to other types. As a result of heat release, the refrigerant condenses into a liquid. The main goal is to have the refrigerant at the same pressure when it leaves the condenser but cooler.

Industrial refrigeration uses three types of condensers:

Air-cooled – This method involves exposing the refrigerant to outdoor air to achieve cooling, utilizing a fan or blower to distribute the air across the entire area.

Water-cooled – A second tube containing refrigerant is usually employed with a water-filled tube. Water absorbs heat from the refrigerant.

Evaporative – This method is commonly used to transfer heat through water spray on the refrigerant coil, resulting in heated and moist air that a fan or blower expelled from the system. It's the most widely used of the three.

Metering Device

After leaving the compressor, the refrigerant enters the metering device. Here, it serves two important purposes. Firstly, it reduces the flow rate of refrigerant into the evaporator. Secondly, it decreases the pressure. Essentially, this device acts as a valve between the high and low-pressure components of the refrigeration system.

Evaporator

The final stage of the cycle involves the absorption of all unwanted heat. Like the condenser, this component is also a coil, but the refrigerant evaporates in this case. In industrial settings, the options for cooling are either air coil evaporators or liquid coolers.

Refrigerants

Refrigerants are liquids used to transfer heat between areas. These substances change form due to variations in temperature and pressure. For example, as the system's temperature increases, it transitions into a gaseous state. When it loses heat, it returns to its liquid form. As a result, the refrigeration cycle of heating and cooling is created.

Industrial refrigeration commonly uses ammonia and R-134a. R-134a is halogen-free and environmentally friendly. Ammonia is an older refrigerant but more efficient at absorbing heat. Other refrigerants available are carbon dioxide, hydrocarbons, and fluorocarbons.

The Use of Natural Refrigerants

As one of the key components, refrigerants have a significant role in the industrial refrigeration cycle. Many companies have switched to natural refrigerants in recent years.

The use of natural refrigerants in industrial refrigeration has become increasingly popular in recent years. Ammonia, carbon dioxide, and hydrocarbons are natural refrigerants with a lower environmental impact and are more energy-efficient than traditional synthetic refrigerants.

Types of Natural Refrigerants

There are three categories of natural refrigerants, as follows:

Carbon Dioxide (CO2) or R-744

This substance is frequently utilized in the automotive sector as a substitute for Hydrofluorocarbons (HFCs) due to its lack of impact on the ozone layer and low potential for global warming. It lacks both odor and color and is denser than air. Its Global Warming Potential (GWP) is equivalent to one.

Ammonia (NH-3) or R-717

Ammonia is the most commonly used refrigerant in industrial refrigeration and was previously used in home refrigerators. It's a naturally occurring compound that decomposes into hydrogen and nitrogen molecules, which make up 80% of the atmosphere. The ammonia refrigeration system operates using a closed cycle of evaporation, compression, condensation, and expansion.

Hydrocarbon-Based Refrigerants (HC)

These refrigerants are natural and don't harm the ozone. They have a low global warming potential of less than 5. These gases require expertise and precautions since they are flammable gases (A3 type). There are restrictions on using them as refrigerants with a load limit of 150 grams.

Benefits of Natural Refrigerants

Here are some benefits of using natural refrigerants in industrial refrigeration systems:

Environmentally friendly – Natural refrigerants have a lower GWP than traditional refrigerants such as hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs). They don't contribute to ozone depletion or climate change, making them a more sustainable option.

Energy-efficient – Compared with conventional refrigerants, natural refrigerants require less energy to maintain the same level of cooling. This results in lower operating costs and reduced carbon emissions.

Cost-effective – Natural refrigerants' availability and lower GWP make them more cost-effective than conventional refrigerants. They also require less maintenance and have a longer lifespan, resulting in lower repair and replacement costs.

Safe – They're non-toxic, non-flammable, and non-corrosive, making them safer to handle and use than traditional refrigerants. They also have a lower risk of leakage, which reduces the risk of accidents and environmental damage.

Industrial Refrigeration Service and Maintenance

Neglecting maintenance can lead to costly breakdowns, lost productivity, and product spoilage. That's why having a reliable industrial refrigeration service provider is essential to keep your system in top condition.

Regular preventive maintenance can include checking refrigerant levels, inspecting electrical connections, cleaning coils, and replacing worn or damaged components. In addition, a service provider can perform preventative maintenance to identify potential problems before they become serious.

Commercial refrigeration – An overview of current status

Commercial refrigeration comprises food freezing and conservation in retail stores and supermarkets, so, it is one of the most relevant energy consumption sectors, and its relevance is increasing. This paper reviews the most recent developments in commercial refrigeration available in literature and presents a good amount of results provided these systems, covering some advantages and disadvantages in systems and working fluids. Latest researches are focused on energy savings to reduce CO2 indirect emissions due to the burning of fossil fuels. 

They are focused on system modifications (as dedicated subcooling or the implementation of ejectors), trigeneration technologies (electrical, heating and cooling demand) and better evaporation conditions control. Motivated by latest GWP regulations that are intended to reduce high GWP HFC emissions; R404A and R507 are going to phase out. Besides hydrocarbons and HFO, CO2 appears as one of the most promising HFC replacements because its low contribution to global warming and high efficiencies when used in transcritical and low-stage of cascade systems.

Introduction

Commercial refrigeration comprises all equipment used by retail outlets (supermarkets and food sales) for preparing, holding and displaying frozen and fresh food and beverages for customer purchase (IPCC/TEAP, 2005). Approximately half of the energy consumption in a supermarket is associated with the refrigeration system (Rivers, 2005). Supermarkets produce a significant global warming impact due to greenhouse gases (GHG) emissions: indirect CO2 emissions from electricity generation in power stations and high GWP (Global Warming Potential) HFC direct emissions, leakaged from vapour compression systems (James and James, 2010).

On the one hand, refrigeration systems performance (related to refrigerant choice, system design and selection) affects greatly to the CO2 emissions (Söğüt, 2015). Fifteen percent of the electricity consumed worldwide is used for refrigeration and the cold-chain accounts for approximately 1% of CO2 emission in the world (Tassou et al., 2011). Braun et al. (2014) carried out a regression analysis and predicted that the 2030–2059 electricity consumption is thought to rise by up to 5.5% with 2.1%, being the central estimate. The study realized by Gschrey et al. (2011) concludes that contribution of F-gases to global warming will increase from approximately 1.3% (2004) to 7.9% (2050) of projected total anthropogenic CO2 emissions.

On the other hand, commercial refrigeration systems that use HydroFluoroCarbon (HFC) contribute to a large degree to the greenhouse effect (Koronaki et al., 2012): The annual leak rate for stand-alone and medium & large commercial applications is 2% and 11%, respectively. Besides, the typical refrigerant charge varies between 3 and 30 kg; and 30 and 300 kg, respectively.

At present, the HFC R404A and R507A (Arora and Kaushik, 2008) are the refrigerants most extended in commercial refrigeration in developed countries for freezing and conservation needs. They replaced the ozone-depleting HydroChloroFluoroCarbon (HCFC) R22 and R502 due to the Montreal Protocol application (UNEP, 2007), even though they present lower energy performance (Messineo et al., 2012, Ge and Cropper, 2008).

Due to European F-gas regulation (Regulation (EU), 2014), high GWP refrigerants (as R404A and R507A) are going to be phased out in most of refrigeration and air conditioning applications, in order to reduce GHG direct emissions. This regulation will produce relevant changes in existing European commercial refrigeration systems (Mota-Babiloni et al., 2015), Table 1.

This paper aims to provide the current state of the art of commercial refrigeration, covering different important aspects related to energy consumption and GHG (CO2 and HFC) emission savings, since commercial refrigeration is one of the applications most contributing to the global warming. In section 2, this article reviews the last investigations on supermarket energy consumption analysis and models. In section 3, the latest developments in supermarket models are presented. In section 4, the recent refrigeration cycle improvements are collected. In section 5, last studies on trigeneration are shown. In section 6, the HFC replacements are shown. Finally, section 7 contains the main conclusions of this paper and future recommendations.

Section snippets

Supermarket energy consumption analysis

Some energy savings methods are easily achievable with very low paybacks (less than 3 years) (Evans et al., 2014a), even though the modifications must be analyzed individually for each situation to fully optimize performance and therefore to maximize energy savings.

Some basic parameters can play an important role on final supermarket energy consumption. Mossad (2011) highlights the great relevance of design, commissioning and maintenance phases to reduce the energy consumption in refrigerated

Control

In addition to analyze supermarket energy consumption, freezing and conservation control is another energy saving method that does not produces system modifications, and therefore less expensive than others. A good control of operating conditions is necessary to obtain optimum food and beverages quality and it. Although the temperature control of food products in supermarkets (or food stores) is essential, it is proved that this regulation is not thoroughly done (Lundén et al., 2014).

Refrigeration cycle improvements

This section reviews some basic cycle improvements for energy performance increase. Last efforts are intended to develop subcooling and ejector technologies. Other recent basic cycle modifications developed to increase energy efficiency are also identified and reviewed in this part.

Trigeneration

Supermarkets have electrical, heating and cooling consumption. They can be supplied together providing energy savings beyond only optimize or modify refrigeration cycle. As Fricke (2011) asserts, one of the most interesting options from an economic and energetic point of view is to consider heat recovery systems.

Trigeneration supermarket studies using CO2 as working fluid of the refrigeration cycle are very common. In a microturbine trigeneration system (Ge et al., 2013), this system can

High-GWP HFC replacement

Since detrimental effect of HFC emission over the atmosphere was discovered, they were intended to be replaced by fluids with lower GWP values. R404A and R507A present a GWP of 3922 and 3985 (Solomon et al., 2007), being two of the refrigerants most commonly used with highest GWP.

The investigations about replace currently used refrigerants are focused on finding safe, stable, energy efficient and environmental friendly replacements (drop-in or retrofit alternatives if possible) (Calm, 2008).

Conclusion

Commercial refrigeration systems are one of the most relevant sectors in terms of energy consumption and Greenhouse gas emissions to atmosphere. This paper reviews the state-of-art of recent developments and contains and covers important topics such as supermarket refrigeration system energy efficiency, GHG emission control regulations, HFC phase-out and low GWP alternatives. The main conclusions of the study are the following ones.

Commercial refrigeration technology is improving slowly and

Acknowledgements

The authors thankfully acknowledge "Ministerio de Educación, Cultura y Deporte" for supporting this work through "Becas y Contratos de Formación de Profesorado Universitario del Programa Nacional de Formación de Recursos Humanos de Investigación del ejercicio 2012".