hlađenje supermarketa: propan kao rashladno sredstvo

Dipl.-Ing. Slobodan PejkovićE-mail: [email protected]

Serbian HVAC & R Society - Technical Committeefor Refrigeration, Heat Pumps and Energy Efficiency

Supermarket refrigeration: Propane refrigerant R290, air-to-water heat pumps, water-to-water chiller,self-contained display cabinets and self-contained mono-block refrigeration units in the same location

Hlađenje supermarketa: propan kao rashladno sredstvo, vazduh-voda toplotne pumpe, voda-voda

toplotna pumpa, rashladne vitrine i monoblok rashladni agregati, sve na jednom mestu

48th International HVAC&R Congress – Belgrade 2017

Session 6: Refrigeration Machines and Systems

mailto:[email protected]

Supermarket refrigeration: Propane refrigerant R290, air-to-water heat pumps, water-to-water chiller,self-contained display cabinets and self-contained mono-block refrigeration units in the same location

The message of this presentation should represent the recommendations on how to safely use propane in

refrigeration and air conditioning systems before the introduction of the new necessary legislation.

The question is how to manage health and safety risks associated with the design, manufacture, installation,

use and maintenance of refrigeration and air conditioning equipment with flammable refrigerants.


Propane refrigerant R290 - Supermarket refrigeration 2

One of the world’s biggest retail chains has decided to open 20 supermarkets in Serbia, each with over

2000m2 net surface area, of which the store sales area covers approximately 1400m2. The supermarkets

are under construction across Serbia, but none of them will be opened before the beginning of 2018.

The first supermarket that has already been fully completed is located in Belgrade and its different

systems and installations are being subjected to trial testing.

The adopted concept is based on refrigeration installations with propane as a refrigerant.

The refrigeration installations in this building have been constructed based on incomplete design

documentation.



Propane (R290) is the most commonly used hydrocarbon refrigerant.

Hydrocarbon (HCs) refrigerants face restrictions because of their high flammability. Highly flammable fluids are very easy to ignite and can burn with explosive impacts.

R290 is a refrigerant with excellent thermodynamic properties and it is becoming an attractive natural refrigerant choice for distributed system architectures such as self-contained display cases, cold room units and centralized systems like secondary systems or refrigeration medium temperature chillers with a glycol loop.

Hydrocarbons are designated as Group A3 refrigerants. The capital letter (A) indicates the toxicity (low toxicity) and the numeral denotes the flammability (3 – highly flammable).

Small factory-sealed appliances can have a Group A3 (flammable refrigerant) charge of up to 150g in each separate refrigerant circuit, and can be located anywhere without restriction. It is permissible to have numerous systems, with charges less than 150g, located in the same area.



One part of the refrigeration installation is located within the building,

while the other part is outside the building.

The indoor equipment includes:

Cold rooms for fruit, vegetables, meat, dairy products (working temperature from +2°C to +10°C), and frozen products (working temperature -24°C), that are refrigerated using self-contained monoblock refrigeration units for roof-top installation; plug and play type system design with a water cooled condensers.

Refrigerated display cases for MT-medium temperatures (Design with a water cooled condensers)

Refrigerated display cases (islands) for LT- low temperatures (Design with air cooled condensers)



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Heat pumps and a chiller are located outside the building.

On the platform next to the building there are two air-to-water heat pumps, and on the roof there is one water-to-glycol/water chiller.

On the platform next to the heat pumps, there are also two dry coolers that may be a source of ignition and fire.

Dry coolers should have been installed at least 10m away from the heat pumps, while the platform with the heat pumps should have been constructed so as to prevent pooling of propane in the event of leakage.

The flammable refrigerants are heavier than air and can tend to pool at floor level.

HEAT PUMPS DRY COOLERS

CHILLER

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Amount of propanewithin the building

- cold rooms -

Total amount of R290,

in all three cold rooms,

is 2550g.

Self-contained monoblock refrigeration units for roof-top installation at positive and negative temperatures in the cold room.

No For t[°C] Pcs/cir R290/cir R290 tot

1 fruit&vegetables +8 1/2 145g 290g

2 meat&dairy products +2 2/2 145g 580g

3 frozen products -24 4/3 140g 1680g

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The main concern is the potential for re frigerant leakage and subsequent

ignition. The cold room spaces are well sealed. Flammable zones can exist in

poorly ventilated rooms.

The area is not ventilated for purpouse of R290 installation.

The presented cold rooms do not have an installed ventilation system that

would, in the event of a propane leak from the installations, suck the gas and

discharge it outside the building (into the open air). The installed equipment

meets the regulations according to which each separate refrigerant circuit has

less than 150g propane charge.



The allowable charge of a flammable refrigerant in a system represents the maximum

amount that could discharge into an occupied space due to a leak.

In EN378:2016 the amount of refrigerant permitted in a “human occupied space” for a

refrigeration application is:

20% x LFL x Room volume

Where:

LFL – Lower flammability limit - minimum concentration of the refrigerant that is

capable of propagating a flame through a homogeneous mixture of refrigerant and

air measured at 21°C and 101.3 kPa (in kilograms per m3 of the space)

For propane, LFL = 0.038 kg/m3



When determining refrigerant charge limitations ensure that it is the “net” volume of the space that is used. For cold rooms, net volume means the room volume after deduction of the stock volume. For example, in a cold room for fruits and vegetables with a total volume of 50.6m3 that can be stocked up to 60% of the room volume.

The maximum charge for R-290 (propane) is:

0.2 x 0.038 x (0.4 x 50.6) = 0.154kg

This shows that the maximum permitted propane charge for this size of a cold room is 154g, which is above the permitted charge for a separate refrigerants circuit. The installed refrigeration unit has 2 x 145g, which is permitted, but it would still provide need for forced ventilation, because of a possible propane leak, or even better solution, an indirect cooling system with glycol/water mix.

If systems with the flammable refrigerants cannot be made or installed to conform to these limits, then indirect systems must be used.



Amount of propanewithin the building

- sales area -

The sales area is equipped with two groups of refrigerated display cabinets (5 + 4), a total of nine display cabinets, operating at temperatures above zero.

Total amount of propane therein is 5 x 3 x 80g + 4 x 3 x 80g, which totals 2160g.

Additionally, there are 14 + 6 display cases (islands) for frozen products with 100 and 110g charges.

The total amount of propane therein is 14 x 110g + 6 x 100g, which totals 2140g.

The total amount of propane in the sales area is 4.3kg.



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Chiller on the roof

The chiller located on the roof with 1.9 kg charge

is near the ventilation grilles for fresh and exhaust

air. In the event of a propane leak from the chiller,

a mixture of fresh air and propane enters the air

handling unit and may cause a fire.

Usually air handling unit has not been made with

“flameproof” electrical equipment.

Suggested solution is that the ventilation grille for

fresh air suction should have been placed away

from the chiller.

Propane refrigerant R290 - Supermarket refrigeration


14

The chiller was designed to cool two rooms with electrical equipment(a server room and a room with UPS equipment), and it must operate throughout the year.

Cooling capacity at design point14.7kW

Total power input 8.4kW

The chiller was designed with a water cooled condenser. It is a plate heat exchanger - PHE and it is connected with dry coolers via glycol pipeline.

The same pipeline is connected with the condensers of refrigerated display cabinets that operate at medium temperatures, as well as with the condensers of monoblock units.

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The design could have provided a more energy efficient solution with direct free

cooling. Thus the introduction of cold air into the space would enable cooling

without compressor operation until the outdoor temperature reaches +20.

The requirement is to maintain room temperatures up to 27°C.

At higher temperatures the space would be cooled using fan-coil units connected

with a cold water of the air conditioning system.



Microchannel HE cannot be used with HP

Heat pumps – HP were designed for the requirements of the sales area air conditioning. There are two heat pumps, each with 11.8kg propane charge.

Propane-based HPs mainly have low cooling capacity.

For many years there have been chillers with air cooled condensers for outdoor installation. Condensers are microchannel heat exchangers made of aluminium, and they are highly efficient.

As for their construction, the space volume on the refrigerant side is small and it requires low propane amounts.

Since they are used for cooling only, they usually operate at lower condensing pressures than HP.



Microchannel HE cannot be used with HP, since the ice forming on the outer finned surface would destroy

the fins. Therefore, the manufacturers of heat pumps install or apply Cu-Al heat exchangers, which are

bigger and which require larger propane charges.

In order to provide the required water temperature during the winter period of heat pump operation, the

system must operate at higher condensing pressures (up to 20 bar), and thus the leakage possibility is

higher.

At outdoor temperatures of 40°C, condensing pressure can also be up to 20 bar.

For this reason and because of a larger charge amount, heat pumps and chillers should be installed

outdoors, in a secured area without the equipment which could be a source of ignition, and with the

restricted access for unauthorised personnel. Also, the equipment should be grounded in order to

eliminate static electricity.



HEAT PUMPS

DRY COOLERS

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Technical characteristicsof heat pumps

I could not find this document on the Internet.

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Technical characteristics of heat pumps

The presented table is from the manual and it is incomplete. It also contains some inaccurate or, better to

say, unrealistic data.

These are the data for water flow resistance (pressure drop) in the plate heat exchanger.

For the heating capacity in the combined operation with air and glycol as a heat source, there is an

illogical value, if it is compared with the value for the operation when only air is used as a heat source at

temperature of -15°C.

This indicates that due to a fast introduction of new “technologically innovative equipment”, various

mistakes may be allowed.

The installed heat pumps has no Eurovent certificate, and it „can“ operate for heating even below -20°C

(information from the manufacturer’s documentation).

Profit determines the development path and introduces “new technologies” in the refrigeration

techniques. Human safety is not of crucial importance.



HEAT PUMP MIRACLEMany new manufacturers of natural refrigerant based refrigeration equipment who have not been involved in this kind of manufacture until recently send significant advertising messages.

I shall mention some of them:

Glen Dimplex presented a new R290 heat pump – the System Zero HP. Dimplex heat pumps, the most economical and environmentally friendly technology. The new system would use at least two different heat sources, including waste heat. External air is used as the primary heat source. A brine circuit uses other heat sources, such as geothermal energy, and above all waste heat.

„Zero as in zero restrictions, zero difficulty, zero waste, zero problems, zero cost explosions.“

Blupura USA Inc. was the first company that received in 2016 authorization from the U.S. Environmental Protection Agency to sell R290-based water coolers in the United States.

„We feel that natural refrigerants are our mission,” said Blupura representative.

Hecoclima does not simply produce refrigerating and heating machines, but develops means to reach efficiency, energy saving, performance, well-being for people and for the environment we live in.

„We know the past, we create the future,” said Hecoclima representative.

Discount retailer Aldi Nord and refrigeration company Viessmann are rolling out a new cooling and heating system employing propane heat pumps, ice storage and photovoltaics.

“The Viessmann Group is one of Europe’s leading manufacturers of innovative refrigeration solutions. Part of our modernization is to make our branches more energy efficient and sustainable, with a focus on environmentally friendly and natural refrigerants”, you can read on their website.

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Common Causes of Fire Accidents

There have been numerous accidents with natural refrigerants worldwide.

On the pictures you can see a building with two cold rooms and a machine room destroyed in the fire in 2009. Fortunately, there were no human casualties. One fireman who was involved in the fire extinguishing had a minor injury.

The refrigerant used was R22, and not HC.

The fire was caused by defective electrical installations. The cold room size was similar to the size of the cold room in the above described supermarket. When the fire occurred, the installation had been approximately 20 years old. The cold room ceiling made of polyurethane panels plated with aluminium sheet was destroyed first in the fire. The partition wall between the machine room and the cold room also burned and disappeared in the fire.

Polyurethane is a flammable material.

On the picture you can see the evaporator with copper pipes and aluminium fins. The fins burned, and copper pipes and steel structure were distorted.

This is the reason why caution must be taken when determining the field of application for hydrocarbons.

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The fire was caused by defective electrical installations

Polyurethane is aflammable material

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Aluminium fins?

Cold Room Door

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EU Level Standards and Legislation for flammable refrigerants

- Refrigerating and air conditioning systems, if not properly designed, constructed, installed, operated and maintained, can be of danger to the health and safety of persons.- Product and equipment manufacturers, installers and end-users need to comply with a complex range of legislation, codes and standards that apply at EU level to all Member States.

- National regulation differs from country to country.

- IEC standards establish a universal charge limit of 150g for commercial refrigeration systems and domestic refrigerators. Small factory-sealed appliances can have a flammable refrigerant charge of up to 150g in each separate refrigerant circuit, and can be located anywhere without restriction. It is permissible to have numerous systems, with charges less than 150g, located in the same area. The basic safety premise is that in the advent of a leak of the flammable refrigerant, the probability of ignition from an external ignition source in the surrounding is very low. However, it is still prudent to locate the systems or appliances away from any known ignition sources. These small systems cannot have any potential ignition sources located within the appliance itself.- For individual systems with flammable refrigerant charges above 150g other specific conditions apply, such as charge limits related to the occupancy, the room volume, the requirement that no sources of ignition are within or in close proximity to the system, and/or minimum ventilation requirements.- EU Directives are mandatory. Use of the standards is not mandatory but it is widely accepted that adherence to a relevant EU standard is an important way of showing that the equipment is safe to use.- Important safety standards, like ANSI/ASHRAE 34, ANSI/ASHRAE 15 and EN 378, were updated in 2016.

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The diagram shows the propane charge limits that can be used “for human comfort” depending on the floor area of the space occupied by people. The diagram has been taken from the latest version of EN 378:2016. According to this diagram, the maximum permitted charge for propane is 1.5kg. This should refer to one refrigerant circuit.

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Within another few years it is likely that codes will be revised again, to take into account practical

experience and new research. These may allow even larger charges to be used, although that clearly

depends on the nature of the experience gained.

Researchers at the National Institute of Standards and Technology (NIST - part of the U.S.

Department of Commerce; NIST is one of the nation's oldest physical science laboratories) have just

completed a multiyear study to identify the "best" candidates for future use as air conditioning

refrigerants that will have the lowest impact on the climate.

In other words, the NIST study found no ideal refrigerant that combined low "global warming

potential" (GWP) with other desirable performance and safety features such as being both

nonflammable and nontoxic.

HC experts agree that R290 refrigerants must be used with care due to the flammability risk.



On the other hand, we have the following:

On a global level, the International Electrotechnical Commission (IEC), through its SC61C Sub-Committee Working Group (WG4), is working on raising the charge limit for flammable (A3) refrigerants. The new maximum charge under consideration for propane, is 500g for small factory-sealed appliances in each separate refrigerant circuit.

I would like to remind you the 150g is the maximum charge that is currently permitted.

“The chances are we’ll finalize this by the end of 2017 and publish the standard in 2018,” said Marek Zgliczynski, chairman of the SC61C sub-committee.



Propane is an attractive refrigerant for the outdoor-use of the integral plant

on the primary side of the secondary systems to make it completely natural.

That is the ideal choice to avoid refrigerant leaks in the cold rooms.

For the propane chiller, there is no charge limit in a many countries if the

propane is confined placed to outside the building or to a machine room.

Hydrocarbon chillers are cheaper to manufacture than ammonia chillers as

they rely on the same or similar components as synthetic refrigerants and are,

therefore, more attractive for lower capacities.



Recommended Process - Solutions for Secondary Systems

Refrigeration in this building could have been solved without flammable fluids within the building.

For the cooling or air conditioning of rooms with electrical equipment, during the winter period direct free-cooling could be used, and during the summer period the space could be air conditioned using fan-coil units connected with the air conditioning system.

The cold rooms and display cabinets operating at medium temperatures should be connected with the chiller with air cooled condenser using R290 as a refrigerant with the secondary glycol-water circuit at temperature of -6°C.

The cold rooms and display cases operating at low temperatures should be equipped with cooling units using CO2 as a refrigerant with a water cooled condensers, and the condensers should be

connected with the same chiller that operates with the secondary glycol-water circuit with temperature of -6°C.

A part of the chiller’s waste heat should be used for floor heating using a partial heat recovery.

Cold/hot water production for air conditioning of the building should be provided using air to water heat pumps with R290.

All the equipment containing flammable fluids would be located outside the building, on a specially separated area with no access for unauthorised personnel.



Conclusions: All refrigerants are dangerous if misused or applied incorrectly.

Propane is the best refrigerant if used properly.

Choosing a refrigerant requires more knowledge. That part of the job should be the responsibility of designers who have not undergone the training for work with flammable refrigerants.

Designers, manufacturers, installers and service technicians of plants must ensure that flammable refrigerant-based systems or plants minimise the risks to the health and safety of persons.

Inadequately qualified personnel pose the risk of accidents. It is, therefore, essential that the personnel dealing with such systems be competent.

A competent person is a person who has acquired through training, qualification or experience, the knowledge and skills needed to carry out the task. Less than five percent of technicians dealing with refrigeration equipment servicing and maintenance in EU have undergone the training for work with flammable refrigerants.

It is necessary to constitute an international platform for exchange of knowledge and experience regarding flammable refrigerant-based systems or plants.



Thank You For Your Attention

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