We all know that supermarkets use five times more energy per square foot as compared to any other commercial building and they are considered somehow complex applications for heating, ventilating and air conditioning systems, etc.
Supermarket HVAC Design
In case the indoor air conditions are very hot, all the products get spoiled, very dry in a way that products shrink, too wet in a way products mold, too cold and your customers complain. Every professional involved in a supermarket’s HVAC design cut energy costs, ensure food and customer safety so that they can provide the proper amount of fresh, healthy outdoor air at the precise temperature and humidity necessary for the space. With every professional designer, stores realize higher sales, lower operating costs, and better indoor air quality for all occupants.
Supermarkets have a unique mix of applications housed under one roof. Each application may have specific HVAC requirements to heat and cool the space as well as provide the required amount of ventilation air. In one part of the store, refrigerated cases provide a steady stream of cool air into the aisles, on the other side, cooking equipment rejects heat that must be exhausted from the store. The exhaust volume alone can dictate a large outdoor air intake to keep positive pressure in the space. In addition, people and cooling loads fluctuate continuously during store operating hours.
Effective Strategies for HVAC Design Systems
Effective Supermarket HVAC Design
These are few supermarket HVAC design standards.
Air Curtain HVAC systems
Let’s assume that the first thing we notice when we enter a store is the air curtain. That is the blast of air you feel when you enter any building. If it is a large store, we might also find them in the loading bays too. These air curtains are suspended above the doorway, or it might be built into the ceiling. Inside the unit is a blower fan which is driven by a small electric motor, this forces air into a funnel to provide a powerful jet of air. You can also get versions that provide heated and or cooled air.
For heating or cooling, we can use a heat pump which uses a refrigerant in order to heat or cool the air which depends on the seasons. Furthermore, we can integrate this into a VRF heat recovery system to provide heating and cooling to different parts of the store. We’re going to look at this in greater detail a little later in the article.
This air curtain actually creates a barrier between the indoor and outdoor air, the two will be at different temperatures and humidifies.
Main Supermarket Ventilation
The very next thing we notice is the forced ventilation that is there around the store. In a lot of large supermarkets, you will see the ductwork for this suspended from the ceiling. The ducts come from either Air Handling Units or Rooftop units. Both do a very comparable role although rooftop units are more common in supermarkets simply because they are an all-in-one HVAC solution.
Rooftop Units
As the name tells us, rooftop units are obviously located on the roof of the supermarket, and you will usually find multiple units that depend on the size of the store. Inside the unit is a large fan which usually pulls fresh air into the unit and also pushes this into the building, some units use this pushing force so that they can push the dirty used air out of the building. The air passes through a filter to remove any dust and dirt, it then passes through a heat exchanger where it will be heated or cooled in order to meet the required conditions.
- For heating, the rooftop unit uses either an electrical heating element, a gas burner, or a heat pump.
- For cooling the unit will use either a split air conditioning unit or a heat pump.
Air Handling Units
Air handling units usually work in a very similar way although these are usually much larger and typically kept indoors. These units will also filter, heat, cool and humidify the air although the heating and cooling is provided by a remotely connected chiller and boiler. There will also be an exhaust AHU so that they can maintain pressure in the building and extract the used air. If the returning air is within certain limits of C02, humidity and temperature then in this case some of it can be recirculated so that it can reduce the heating or cooling load.
Fan Coil Units
If you look up at the ceiling in large superstores you will see a large box would be connected to a short run of ductwork. This box is basically a fan coil unit. Inside the fan coil unit is a fan that has a small motor, a filter, and also one or two heat exchangers. The fan coil would circulate air locally within the building and top up the heating or cooling to this local area as needed. They would also help to distribute fresh air within the whole building. The fan coil units can provide heating and or cooling and the heat exchangers will be connected to either a heat pump, VRF, split AC, chiller, or boiler.
Extract ventilation
There are going to be some bad odors in the building from places such as toilets, food preparation areas as well as car parks. This bad air has to be extracted from the building, so these will be connected to dedicated exhaust systems. You may also find several of these areas connected into one system or a separate extract for each one. There are several different fans that are used but one of the most common and simplest designs is to use a centrifugal type of fan like this. The fan uses a belt-driven motor to rotate the fan blades and create a pressure difference, this will suck the air in on one side and force it out the other.
Some stores are designed in such a way that they will also use refrigeration systems in order to provide space heating and cooling, these will use systems like VRF, split AC as well as heat pumps.
Split Air Conditioning
Split AC is considered the simplest, it is just a vapor compression system that uses a compressor, a condenser, an expansion valve, and an evaporator. The compressor would push the refrigerant around the system to collect the unwanted heat from the evaporator and bring this over to the condenser. The refrigerant usually has a very low boiling point so as it enters the evaporator, the heat of the room will be more than enough to make it will boil and evaporate.
As the refrigerant evaporates it collects the unwanted heat and carries it away back to the compressor. As the unwanted heat is collected in the evaporator, it is exchanged for a cooling effect. This type of system will only provide cooling.
Variable Refrigerant Flow System
Variable Refrigerant Flow System uses a variable speed compressor as well as some electronic controls and sensors to adjust the amount of refrigerant flowing around the system in order to match the cooling load. This would allow the unit to provide cooling to various locations simultaneously although again this version only provides cooling.
Heat Pumps
The next variation is the heat pump, this would allow the unit to provide cooling or heating, it can also switch between cooling and heating, but it can only provide one of these at a single time. It works by utilizing the reversing valve. This diverts the hot discharge refrigerant from the compressor to either the outdoor unit or the indoor unit depending on whether the unit is in heating or cooling mode. There will likely be multiple expansion valves as well as non-return valves to ensure the refrigerant flows along the correct pipes. In cooling mode it operates like a normal cooling system, collecting the heat from the indoor unit and dissipating this to the atmosphere via the outdoor unit.
In heating mode the system operates in reverse form, that is collecting heat from outdoors and dissipating this indoors. The boiling point of the refrigerant is exceptionally low so even the outside air in winter can cause it to boil and evaporate. Even when it is cold outside, the air, in most cases, will still contain enough thermal energy to boil the refrigerant and therefore provide heating.
How does supermarket refrigeration work?
There is a wide variety of commercial refrigeration systems:
- Reach-in vertical cases and refrigerators
- Plug-in enclosed vending machines
- Semi-vertical display cabinets
- Horizontal cases
- Deli cases
- Drop-in coolers
- Draft beer systems
- Undercounter refrigerators
- Back bar coolers
- Refrigerated display cases
- Prep table
The numerous commercial refrigeration equipment can have different functions:
Chillers
As we know that chillers keep items, for example, food and beverages, that are below the average room temperature yet above freezing. Such equipment prevents spoilage by keeping consumable items cool.
Freezers
Freezers are used for keeping consumable items frozen and preventing them from spoiling.
Combo Chillers and Freezers
Combination commercial refrigeration units usually allow for both chilling and freezing perishable items.
Working of Commercial Refrigeration
The Cooling Process
All refrigeration works on a principle that is called the Second Law of Thermodynamics. This principle basically states that when two objects of different temperatures come close together, heat will always travel from the hotter object to the colder one. As a result of this rule, commercial refrigeration systems would utilize a refrigerant solution in order to transfer heat from the food inside the refrigeration unit’s storage area to the refrigerant.
Refrigerant solutions always obey a second physical principle that is gases cool as they expand and heat up as they compress. While cycling through the refrigeration system, the refrigerant is sent through a series of pressure changes so that they can improve efficiency and speed. It removes heat from the refrigerated space to keep it cold.
The Refrigerant
Always keep in mind that refrigerant is the key to the success of modern commercial refrigeration systems. In the past, Freon was the most common refrigerant that was found in both air conditioning units and refrigerators. Though, Freon used to damage the Earth’s ozone layer, which could cause an increase in solar radiation reaching the planet’s surface and changes in the global climate. At present, Freon is out of use in many countries. Other refrigerants, such as tetrafluoroethane, are taking their place so that they can improve the efficiency and eco-friendliness of modern refrigeration systems continually.
The commercial refrigeration system has expanded to a huge industry. The cooling process can be a high-temperature process in order to get the environment to low-temperature freezing. Freezers hold fundamental importance in the food business. If your refrigerating system does not function correctly, that could jeopardize your whole company. Commercial refrigeration presents a challenge to the technicians, owners, and installers who deal with them daily. There are several installations, networks, parts, costs, etc.
Commercial refrigeration systems operate with the help of a circuit that works with an absorption system or vapor compressor in order to cool or dry the air. The general refrigeration principle expands the liquid into a gas, and it would eliminate heat from the local area. One of the simple refrigeration cycle components is the commercial refrigeration compressor.
