Fig。 3。  Isothermal surfaces at Tsup = 17 °C。

and the RAG have a little variation and maintains at about 61% and 87%, respectively。 However, as air temperature increases at con- stant relative humidity, the air moisture content increases。 In other words, it will lead to an increase of latent heat load or electricity consumption inputted into the VORDC。 Fig。 6 shows the variations of electricity consumption both of the HVAC and the VORDC with the  DSAT。  When  the  DSAT  increases  from  16 °C  to  19 °C,    the

Fig。 4。  Temperature field under different supply air   temperature。

X。  Wu  et al。 / International Journal of  Heat and  Mass Transfer 87 (2015)    685–692 689

Table 2

Temperature and relative humidity variations with   Tsup。

Fig。 5。  Comparison of NIR for different supply air temperature,   Tsup。

Fig。 8。  Comparison of products temperature on the second shelf for different   Tsup。

The products temperature is a crucial parameter in controlling the hazard of bacterial development [32]。 In the VORDC, the major- ity of maximum temperature packs (97%) are located at the front of the cabinet, the largest number (60%) being at the front of the base论文网

of the cabinet [33]。 In this paper, the front products on the  second

shelf are predicted in shelf-scale model。 The specific location of

(b)HVAC

Fig。 6。 Electricity consumption of HVAC and VORDC for different supply air temperature, Tsup。

electricity energy input in VORDC system increases 6。36%。 Meanwhile, as is described in Eq。 (8), the HVAC cooling load or electricity consumption decreases。

products is shown in Fig。  7。

From Fig。 8, it can be seen that the DSAT will obviously influ- ence the products temperature。 When the supply air temperature increases from 16 °C to 19 °C, the maximum difference of products is 0。18 °C。 In addition, the temperature of products gradually increases from both sides to the middle due to the effects of exter- nal conditions of VORDC, as is shown in Fig。   9。

690 X。  Wu  et  al。 / International  Journal  of  Heat  and  Mass  Transfer  87  (2015)      685–692

Fig。 9。  Temperature field at H = 0。92 m in shelf-scale  model。

3。2。Influence of diffuser supply air    velocity

As reported in other studies, the infiltration heat transfer rate is also related to the magnitude and the direction of ambient air velocity [2]。 Therefore, the influence of the DSAV of HVAC should be considered。 In the supermarket-scale simulations, it is found that there are two vortexes between air curtain of VORDC and air flow from the diffusers, as is shown in Fig。  10。 At the  interaction of the vortexes, the HVAC system will affect the ambient condition of VORDC。

Table 3 shows the influence of the DSAV of HVAC on the air temperature  and  humidity  of  measurement  point  and  RAG    of

VORDC。 From the results of supermarket and cabinet-scales computation, the temperature and relative humidity in the    ambi-

ent conditions and at the RAG both decrease with the increase of air velocity from the diffusers due to its lower temperature and moisture  content。  When  the  DSAV  increases  from  3。0 m/s     to

3。5 m/s, the decline trend of the temperature and relative humidity is smaller or of no change。 The reason that, with the increase of DSAV (i。e。 provided cool capacity), the indoor air temperature   will