## 1 Introduction  
Open-type refrigerated display cabinets are important parts of retail food stores used to ensure proper food storage and trading, as they help to attract buyers and increase sales [1]. Food products can be stored and displayed to consumers at different temperature levels in such cabinets [1]. The temperature of food products usually varies between \(-\)1 and +7 \({}^{\circ}\)C (3M2 temperature category) as described in BS EN ISO 23953-2 [2] for chilled food application. This temperature category is suitable for storing milk and dairy products, sandwiches, green salad, and cooked meat products, but is not appropriate for storing minced meat and raw meat. The storage of raw and minced meat requires a temperature between \(-\)1 and +4 \({}^{\circ}\)C (3M0 temperature category) as described in BS EN ISO 23953-2 [2]. From a commercial point of view, open-type refrigerated display cabinets have a great advantage because they do not have physical barriers (such as doors) between the buyer and the food, which allows consumers to have free access to the food [1]. However, due to the open design, food products stored inside the display cabinet are isolated from the environment only by one or more cold air curtains. Air penetration due to open design can contribute up to 67-77% of the total heat load of the open-type display cabinet [1, 3]. Freezers with doors consume significantly less energy due to the door barrier [3, 4]. Replacing open-type refrigerated display cabinets with doored ones becomes an alternative and provides many advantages including improved food quality, achievement of energy savings, and reduced temperature fluctuations. The authors of [5, 6, 7] experimentally and numerically investigated closed refrigerated display cabinets under various conditions: with/without doors and at various external air temperatures. However, although the doored display cabinets exhibited higher energy efficiency, open display cabinets are always preferred by the buyers, as open-type cabinets attract them and make it easier for them to reach the food products [8]. On the other hand, improvements can often be made to the design of display cabinets to improve air curtain performance. Numerical simulation is an economic way to better understand these systems and predict their thermal behavior more easily [9]. The authors of [10] presented results of 3D CFD simulation of air flows and temperatures in horizontal open-top display units. In this paper, the effect of the perforated plate was studied, and the porous-jump model is used. [PERSON] et al. [11] numerically investigated the protective properties of the air curtain in a refrigerated truck. It has been found that an air curtain of optimal velocity can reduce energy consumption by about 50%. [PERSON] et al. [1] compared the performance of open-type refrigerated display cabinets with and without air-guiding strips. The results of the CFD simulation showed that the air-guiding strips accelerated the air curtain vertically and the cooling capacity necessary to keep the food cooled was decreased by 34%. [PERSON] et al. [8] proposed using cold shelf innovation with guiding strips to improve the performance of vertical multi-deck refrigerated display cabinets. The results showed energy savings of 16.7 kWh/24 h compared to the conventional cabinet. [PERSON] [12] numerically studied refrigerated display cabinet designs and compared the performance of a single-jet air curtain with the performance of a double-jet one. The simulation results showed that the effective volume of the open-type refrigerated cabinet with a double-jet air curtain can be 13% larger compared to a single-jet air curtain. Many researchers studied the efficiency of open vertical display cabinets by addressing the parameters that have the greatest effect on keeping product temperatures within the correct range [9; 13; 14; 15]. However, most of the CFD modeling studies presented in the literature were developed in 3D configuration and limited to steady-state.