Submitted By vkey95

Words 5785

Pages 24

Words 5785

Pages 24

DOI: 10.5923/j.jmea.20150501.03

Effect of Evaporator Heater Power Input and Refrigerant

Flow Rate on the Performance of a Refrigerator –

Developing Empirical Models

Ali Naif*, Abdulkareem Shafiq Mahdi Al-Obaidi, Mohammad H. Nassir

School of Engineering, Taylor’s University, Malaysia

Abstract Refrigerators normally are systems that are used to preserve perishable goods in a house hold by reducing the temperature of the food compartments. However, refrigerators are also infamous for their high electricity consumptions.

This paper presents first a comparison between theoretical and experimental determination of the tons of refrigeration (TR) of a vapor compression refrigeration cycle (VCRC). Then, it was looked into the derivation of empirical models, grounded on experimental results, which would provide refrigerator designers a reliable mean to check on the impact of each examined parameter on the TR during the preliminary stage of refrigerator design. It was noted that both evaporator heater power input (EHPI) and refrigerant flow rate (RFR) positively affected the tons of refrigeration, while the effects of condenser water flow rate (CWFR) was negligible. A total of three models generated. As the accuracy of the data for all models were about 99.7%, the minute difference had to be looked in to. Hence, Model 1, considering both evaporator heater power input (EHPI) and refrigerant flow rate (RFR), produced a lower range of error compared to model 2 and 3.

This indicated that Model 1 was the best predictor of TR. The outcomes of the final model were within the uncertainty range of 4.82% and-3.14% compared to the experimental results. This was with in the acceptable range of ±10%. The overall model could be enhance by incorporating other significant evaporator side parameter as…...

...sfs (t, log s, v) − e−r(T −t) Kgs (t, log s, v) , s s cv = sfv (t, log s, v) − e−r(T −t) Kgv (t, log s, v), 1 1 1 1 css = fs (t, log s, v) + fss (t, log s, v) − e−r(T −t) Kgss (t, log s, v) 2 + e−r(T −t) Kgs (t, log s, v) 2 , s s s s K csv = fv (t, log s, v) + fsv (t, log s, v) − e−r(T −t) gsv (t, log s, v), s cvv = sfvv (t, log s, v) − e−r(T −t) Kgvv (t, log s, v). So 1 1 ct + rscs + (a − bv)cv + s2 vcss + ρσsvcsv + σ 2 vcvv 2 2 = sft − re−r(T −t) Kg − e−r(T −t) Kgt + rsf + rsfs − rKe−r(T −t) gs + (a − bv)(sfv − e−r(T −t) Kgv ) 1 1 gs K K 1 + s2 v − fs + fss − e−r(T −t) 2 gss + e−r(T −t) K 2 + ρσsv fv + fsv − e−r(T −t) gsv 2 s s s s s 1 2 + σ v(sfvv − e−r(T −t) Kgvv ) 2 1 1 1 1 = s ft + (r + v)fs + (a − bv + ρσv)fv + vfss + ρσvfsv + σ 2 vfvv − Ke−r(T −t) gt + (r − v)gs 2 2 2 2 1 1 2 +(a − bv)gv + vgss + ρσvgsv + σ vgvv + rsf − re−r(T −t) Kg 2 2 = rc. That is, c satisﬁes the PDE (6.9.26). (iii) Proof. First, by Markov property, f (t, Xt , Vt ) = E[1{XT ≥log K} |Ft ]. So f (T, Xt , Vt ) = 1{XT ≥log K} , which implies f (T, x, v) = 1{x≥log K} for all x ∈ R, v ≥ 0. Second, f (t, Xt , Vt ) is a martingale, so by diﬀerentiating f and setting the dt term as zero, we have the PDE (6.9.32) for f . Indeed, df (t, Xt , Vt ) = 1 1 ft (t, Xt , Vt ) + fx (t, Xt , Vt )(r + Vt ) + fv (t, Xt , Vt )(a − bvt + ρσVt ) + fxx (t, Xt , Vt )Vt 2 2 1 + fvv (t, Xt , Vt )σ 2 Vt + fxv (t, Xt , Vt )σVt ρ dt + martingale part. 2 1 So we must have ft + (r + 2 v)fx + (a − bv + ρσv)fv + 1 fxx v + 1 fvv σ...

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... the respective lower power values are to be stated together with the rated power (which refers to the most efficient cooling), Typical specification could be 70% / 100% ONAN / ONAF, or as overload 100% / 130% ONAN / ONAF. ANSI/IEEE â€¦â€¦â€¦ â€¢ Rated voltage for each winding â€¢ For a transformer with tappings: Which winding is tapped, the number of tappings, and the tapping range or tapping step, Whether 'off-circuit' or 'on-load' tap-changing is required, If the tapping range is more than Â±5 %, the type of voltage variation, and the location of the maximum current tapping, if applicable, see IEC 60076 â€“ 1 (2000-04) clause 5.4. Normal specified type of voltage variation is CFVV (constant flux voltage variation) and in special cases VFVV (variable flux voltage variation). But normal operation will often be CbVV (combined voltage variation). â€¢ Highest voltage for equipment (Um) for each winding (with respect to insulation, see IEC 60076-3), Um according standard voltage levels. Specified voltage in some tap changer plus positions may be higher than Um. â€¢ Method of system earthing (for each winding), Page 71 of 197 ABB â€¢ Insulation level (see IEC 60076-3), for each winding, â€¢ Connection symbol and neutral terminals, if required for any winding, If already a connection between different voltage systems exists in the network it is mandatory to specify appropriate connection symbol. In connection symbol YNyn0 the letters â€œNâ€ and â€œnâ€ means neutral points......

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