超市空调系统英文文献和中文翻译(3)

Q T ¼ ðqvAÞDAGðhRAG — hDAGÞ ð5Þ

Q T:SEN ¼ ðqvAÞDAGcP;MðTRAG — TDAGÞ ð6Þ

Q T:LAT ¼ ðqvAÞDAGhfgðxRAG — xDAGÞ ð7Þ

X。 Wu et al。 / International Journal of Heat and Mass Transfer 87 (2015) 685–692 687

Fig。 1。 The length magnitudes in supermarket。

3。Results and discussions

The main purpose of the paper is to investigate the inﬂuence of supply air temperature and velocity of the diffusers of HVAC system on the heat transfer and ﬂuid ﬂow performance of the VORDC。 Thus, the parameters of VORDC are set as constant in supermarket scale computations。 According to the Chinese Standard GB50736-2012, when the height of supply air outlet is less than or equal to 5 m in a comfort air conditioning system, the diffuser supply air temperature (DSAT) difference should not be greater than 10 °C, and the diffuser supply air velocity (DSAV) is appropriately 2–5 m/s。 So, the supply air temperature and velocity are about 16 to 19 °C and 2。0 to 3。5 m/s in the CFD models, respectively。 The computational conditions of supermarket scale models are described in Table 1。

3。1。Inﬂuence of supply air temperature

Fig。 2。 Ambient measurement point for VORDC。

The power requirements of HVAC unit can be pided into four parts: fan, boiler, chiller and radiator。 The HVAC energy consump- tion is calculated depending on outdoor conditions and parts of operating HVAC unit。 In this paper, only the energy consumption of chiller is considered。 The power input to the chiller is expressed in Eq。 (8) [31]:

Tout — Tsup

Fig。 3 shows three-dimensional isothermal surfaces of T = 20 °C, T = 22 °C and T = 24 °C in supermarket scale when the DSAT (Tsup) is given at 17 °C and the ambient temperature (Tamb) is 25 °C, which indicates the inﬂuence area of supply air of HVAC。 It can be clearly seen that the cold air discharged from the diffusers of HVAC system changes the temperature distribution surrounding the VORDC。

Fig。 4 shows the temperature ﬁelds under different DSAT of HVAC。 It indicates that the indoor temperature decreases with the reduction of the DSAT and the temperature surrounding the VORDC also decreases, which will directly affect the operation con- ditions of the VORDC。 At the same time, it also inﬂuences the NIR of air curtains and products temperature inside the refrigerated dis- play cabinet。 Table 2 shows the inﬂuence of the DSAT on the tem- perature and humidity of measurement point and RAG。

From Table 2, it can be seen that the ambient temperature of the

VORDC increases with the rising of the DSAT。 The ambient average

temperature increases about 0。16 °C at the measurement point。 As a result of entrainment of the air curtains, the increasing ambient

Here, Pcond is an energy loss due to the condensation, when the sup-

ply air of HVAC system is cooled below the dew point temperature。

Pcond can be described in Eq。 (9):

temperature causes air temperature rising at the RAG in the cabi- net-scale model。 Fig。 5 presents that the NIR increases from

0。285 to 0。305 with the rising of the DSAT。 This indicates that the

thermal insulation performance of air curtain decreases, which will

make the sensible heat load of the VORDC increase, as is shown in Fig。 6。超市空调系统英文文献和中文翻译(3):http://www.youerw.com/fanyi/lunwen_99302.html