Thermal Conductivity of Liquid Dimethoxymethane and

Publication Date (Web): August 15, 2006 ... had been performed at temperatures from (245 to 385) K and pressures from saturation pressure to 30 MPa...
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J. Chem. Eng. Data 2006, 51, 1743-1748

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Thermal Conductivity of Liquid Dimethoxymethane and Dimethoxymethane + Diesel Fuel at Pressures to 30 MPa Ke Zhang, Jiangtao Wu,* and Zhigang Liu State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an Shaanxi 710049, People’s Republic of China

The measurement of thermal conductivity of liquid dimethoxymethane had been performed at temperatures from (245 to 385) K and pressures from saturation pressure to 30 MPa. The thermal conductivity of the mixtures of dimethoxymethane + diesel fuel had been measured in the temperature range from (275 to 375) K and in the pressure range from (5 to 30) MPa with dimethoxymethane mass fractions of 0.05, 0.10, and 0.15. The transient hot-wire method with a single bare platinum hot wire was used. The experimental data of pure dimethoxymethane and the mixtures with diesel fuel, which had an estimated expanded uncertainty of ( 2.0 % with the coverage factor k ) 2, had been correlated as functions of temperature, pressure, and mass fraction, respectively.

Introduction Dimethoxymethane, a solvent and analytical reagent, is of great importance in pharmaceuticals, aerosols, paints, varnishes, paint strippers, and cleaning, resin manufacture, ion exchange resins, fragrances, and pesticides. It has been recognized as an excellent fuel additive because it can improve fuel efficiency and optimize emissions of diesel engine.1 Recently, the measurement of the thermal conductivity of saturated liquid dimethoxymethane had been reported in the previous literature of our group.2 As an ideal fuel additive, there is an urgent need for the experimental value at high pressures and that of the data of its mixtures with diesel fuel. In this paper, the thermal conductivity of liquid dimethoxymethane was measured at temperatures from (245 to 385) K and pressures from saturation pressure to 30 MPa. The measurements of the mixtures of dimethoxymethane + diesel fuel were performed in the temperature range from (275 to 375) K and in the pressure range from (5 to 30) MPa with dimethoxymethane mass fractions of 0.05, 0.10, and 0.15, respectively.

Experimental Section

Figure 1. Hot-wire assembly: 1, steel cover; 2, Teflon O-ring; 3, flange; 4, Cu O-ring; 5, pressure vessel; 6, Teflon disk; 7, injecting pipeline; 8, spring; 9, leader; 10, platinum wire; 11, seal; 12, effusing pipeline; 13, leads.

The transient hot-wire technique is widely recognized as the most accurate method to measure the thermal conductivity of fluids. In this work, an improved transient hot-wire method apparatus with a single bare platinum wire was used. The fundamental working equation takes the form: q 4π λ(Tr, P) ) d∆T d ln t

(1)

where q is the power input per unit length of wire, λ(Tr, P) represents the thermal conductivity of the fluid at a reference temperature (Tr) and the working pressure (P), d∆T/d ln t is the slope of a linear fit to the ideal temperature rise and the natural logarithm of elapsed time. Detailed descriptions of the transient hot-wire method have been presented elsewhere.2-6 * Corresponding author. E-mail: [email protected]. Fax: +86-2982668789.

Figure 2. Block diagram of electrical system.

A schematic diagram describing the transient hot-wire assembly is shown in Figure 1. The bare platinum wire (10) was 20 µm in diameter and about 90 mm in length, and a spring (8) was used to ensure a constant tension on the wire. The

10.1021/je0601614 CCC: $30.25 © 2006 American Chemical Society Published on Web 08/15/2006

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Journal of Chemical and Engineering Data, Vol. 51, No. 5, 2006

Table 1. Thermal Conductivity of Liquid Dimethoxymethane Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

244.53 244.93 245.11 245.41 245.03 245.05 245.37 244.87 244.61 245.07 244.86 245.18 244.98 244.68 244.43 245.49 244.95 245.05 244.86 244.73 264.64 264.82 264.93 265.51 265.50 264.79 265.18 264.41 264.91 264.33 265.81 264.46 264.55 264.63 265.27 264.34 264.82 265.30 265.60 264.25 284.27 284.56 284.64 284.90 284.62 285.18 285.35 285.03 284.94 284.78 285.03 284.35 284.52 284.18

0.10 0.10 0.10 0.10 4.97 5.05 5.08 5.09 10.0 10.0 10.1 10.1 19.9 20.0 20.0 20.0 30.0 30.0 29.9 29.9 0.10 0.10 0.10 0.10 5.13 5.09 5.05 5.17 10.1 10.1 10.1 10.1 20.0 20.0 20.0 20.1 30.0 30.0 30.0 30.0 0.10 0.10 0.10 0.10 5.14 5.10 5.09 5.01 10.0 10.1 10.1 10.1 20.1 20.2

335.3 443.3 482.7 566.4 482.8 482.8 566.5 443.4 401.2 524.0 481.3 568.5 482.9 405.8 335.4 611.1 482.9 523.9 482.9 443.6 377.0 412.1 448.6 610.6 610.6 412.0 526.4 311.6 486.8 338.1 760.6 372.7 377.0 412.0 567.7 311.5 486.6 610.5 700.8 311.5 290.4 351.4 384.1 453.7 384.0 529.2 569.0 490.6 492.3 453.8 532.4 347.4 384.1 290.4

0.161 0.161 0.160 0.160 0.162 0.163 0.163 0.164 0.165 0.165 0.166 0.167 0.169 0.170 0.169 0.169 0.171 0.171 0.171 0.172 0.154 0.153 0.153 0.153 0.155 0.155 0.155 0.156 0.157 0.159 0.158 0.158 0.162 0.162 0.161 0.162 0.165 0.165 0.165 0.165 0.145 0.145 0.146 0.145 0.148 0.148 0.147 0.148 0.150 0.150 0.150 0.149 0.154 0.155

285.05 285.36 284.56 284.78 285.35 284.81 304.55 304.77 305.05 305.56 305.35 305.49 305.80 305.03 304.45 305.01 305.17 304.76 305.82 304.31 304.54 304.93 304.38 304.22 304.94 305.12 324.26 324.49 324.60 324.89 324.71 324.82 325.57 324.95 324.44 324.79 325.11 324.93 324.57 325.26 324.81 325.48 324.48 325.25 324.24 324.65 345.32 345.04 344.39 345.06 344.85 345.00 344.67

20.2 20.2 29.9 29.9 30.0 30.0 0.17 0.17 0.17 0.17 5.09 5.09 5.05 5.09 10.0 10.0 10.2 10.2 20.0 20.1 20.1 20.0 30.0 30.0 30.0 30.0 0.25 0.25 0.25 0.25 4.92 4.92 4.92 4.97 10.0 10.0 10.0 10.1 20.0 20.0 20.0 20.1 30.0 30.0 30.1 30.1 0.12 0.12 0.29 0.29 5.05 5.01 5.01

529.2 610.5 418.2 490.7 610.6 453.7 300.5 360.4 425.6 534.2 496.9 534.4 613.3 425.9 300.5 425.9 460.5 360.4 654.9 272.7 329.9 425.9 300.6 272.6 460.6 496.8 231.6 282.8 310.5 369.4 339.3 369.4 539.4 400.8 282.8 369.4 433.5 400.8 339.3 502.8 400.8 577.2 339.3 539.4 282.8 369.5 442.1 378.8 242.7 379.1 349.5 379.1 293.7

0.154 0.154 0.157 0.157 0.157 0.158 0.138 0.137 0.138 0.136 0.139 0.139 0.139 0.139 0.143 0.143 0.142 0.142 0.146 0.146 0.146 0.146 0.150 0.150 0.149 0.150 0.129 0.130 0.130 0.129 0.132 0.131 0.130 0.131 0.135 0.135 0.133 0.134 0.138 0.138 0.139 0.139 0.143 0.141 0.144 0.142 0.122 0.121 0.121 0.120 0.123 0.122 0.123

344.37 345.38 344.57 344.45 344.91 344.45 344.58 344.75 344.92 344.49 344.14 344.45 344.71 365.12 365.39 364.94 364.81 364.51 364.92 364.80 365.28 364.66 364.80 364.10 364.18 364.41 363.90 364.87 365.04 365.07 363.93 364.92 364.41 384.44 384.83 384.96 385.26 384.11 384.19 385.22 384.80 384.16 384.26 385.14 384.16 384.69 384.75 384.42 385.23 384.61 384.87 384.45 384.17

5.01 10.0 10.0 10.1 10.1 20.0 20.0 20.0 20.0 30.0 30.1 30.1 30.1 0.79 0.79 0.79 0.79 4.96 4.97 5.09 5.09 10.0 10.0 10.1 10.1 20.1 20.1 20.1 20.1 29.8 29.9 29.9 29.9 0.95 0.95 0.95 0.95 4.88 4.92 4.92 5.01 9.92 9.94 9.96 9.93 20.1 20.1 20.1 20.1 30.0 30.0 30.1 30.1

242.7 475.7 293.7 267.6 379.1 293.7 321.0 349.5 410.1 321.0 242.8 321.0 379.2 450.2 516.8 418.6 388.1 330.7 418.6 388.1 482.9 388.1 418.6 253.2 278.0 358.9 229.7 450.2 483.0 516.8 253.2 483.0 358.9 288.5 368.6 397.6 458.7 240.5 264.0 458.6 368.6 288.5 458.7 368.6 264.0 347.9 307.7 422.9 269.5 408.7 470.1 374.4 305.7

0.124 0.126 0.127 0.126 0.126 0.132 0.132 0.131 0.131 0.134 0.136 0.135 0.135 0.114 0.114 0.113 0.114 0.116 0.115 0.114 0.116 0.118 0.119 0.118 0.119 0.124 0.123 0.123 0.124 0.127 0.129 0.127 0.127 0.106 0.105 0.105 0.106 0.108 0.107 0.108 0.107 0.111 0.111 0.111 0.111 0.116 0.115 0.115 0.116 0.121 0.121 0.120 0.121

calibration of the resistance-temperature relation of the platinum wire was carried out in the temperature range from (245 to 385) K by the F18 precision thermometry bridge. To compensate for the end effect, two potential leads (9) of the same platinum wire were welded at the positions about 10 mm to each end of the wire. The pressures of liquids in the cell were achieved by a HPLC pump with the pressure readings acquired. The measuring liquids injected from pipeline (7) and effused from pipeline (12). The liquids pressure changed not exceeding 138 Pa‚s-1 and was accurate within ( 1.0 %. The volume of sample employed in one measurement was about 60 mL including that in the pipelines. The block diagram in Figure 2 shows the data acquisition system used in the present work. It contains some improvements in comparison with refs 2 and 3. (i) The conventional power supply was replaced by a Keithley 2400 sourcemeter, which can be well-controlled by a computer as a constant voltage

source. (ii) The Keithley 7001 switch systems were introduced to the circuit as the switches with a low noise and controlled easily by the computer. All the data acquisition and instrument control were performed by a computer via the IEEE-488 interfaces. The transient hot-wire apparatus was immersed completely in a thermostatic bath. The methyl silicone oil was selected as the bath fluid for the temperature range from (243 to 403) K. The total uncertainty of temperature for thermal conductivity was less than ( 10 mK‚h-1 (ITS90) with a coverage factor of k ) 2. More details about the thermostatic bath and temperature measurement system have been described in previous works.7,8 The performance of the apparatus was tested by measuring the thermal conductivity of saturated liquid toluene from (245 to 385) K, which agreed with recommended values9 within a maximum deviation of 0.78 % and a standard deviation of 0.37 %.

Journal of Chemical and Engineering Data, Vol. 51, No. 5, 2006 1745

Figure 3. Temperature dependence of the thermal conductivity of dimethoxymethane at different pressure: ], saturation pressure; g, 5 MPa; 4, 10 MPa; 3, 20 MPa; 0, 30 MPa.

Figure 5. Relative deviations of calculated values by eq 2 from experimental data for pure dimethoxymethane: 0, saturation pressure; ], 5 MPa; 4, 10 MPa; g, 20 MPa; 1, 30 MPa.

Figure 4. Pressure dependence of the thermal conductivity of dimethoxymethane at different temperature: 0, 385 K; O, 365 K; 4, 345 K; 3, 325 K; ]305 K; g, 285 K; 1, 265 K; b, 245 K.

Figure 6. Comparison of the present data with the previous work:2 0, this work; O, previous work.

Table 2. Coefficients aij/W‚m-1‚K-(i+1)‚MPa-j Used in Equation 2 j)0 i)0 i)1

j)1 10-1

2.589 × -4.002 × 10-4

10-4

4.787 × 2.178 × 10-7

j)2 -1.224 × 10-5 2.753 × 10-8

Results and Discussion The sample of dimethoxymethane was provided by Shanghai Yongfu Aerosol Manufacturing Co. Ltd. The sample was further purified with sodium wire, followed by fractional distillation from sodium. Finally, the mass fraction purity of dimethoxymethane was better than 99.6 %, as indicated by analysis with the Agilent 6890N gas chromatograph. The sample of diesel fuel was the 0# commercial diesel fuel provided by China Petroleum & Chemical Corporation. Its mass compositions were 72.86 % alkane + alkene and 27.14 % aromatic hydrocarbon. The cetane number and its freezing point were 48 and 273.15 K, respectively. The details can be referred from China Standard of GB 252-2000. Dimethoxymethane. Table 1 lists the thermal conductivity of dimethoxymethane in the temperature range from (245 to 385) K and pressure range from saturation pressure to 30 MPa. The temperature rise of the wire in each measurement was about

Figure 7. Relative deviations of the experimental results from the previous work.2

(1 to 3) K. The temperature dependence of the thermal conductivity of dimethoxymethane at different pressures is plotted in Figure 3. Figure 4 illustrates the pressure dependence of the experimental results of dimethoxymethane at different temperatures. The approximating lines in Figure 3 and Figure

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Journal of Chemical and Engineering Data, Vol. 51, No. 5, 2006

Table 3. Thermal Conductivity of Dimethoxymethane + Diesel Fuel; w ) 0.05 Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

275.13 275.32 275.32 276.06 294.90 296.32 295.66 294.64 316.13 314.80 315.94 314.67 334.71 335.52 336.14 335.70 355.97 354.77 356.22 354.67 375.86 375.88 375.14 375.18 275.12 275.72 275.87 275.28 295.61 295.06 295.42 295.22

4.92 4.97 5.05 5.05 4.92 4.97 5.01 5.05 5.09 5.09 5.09 5.09 4.97 4.97 4.97 5.05 4.97 4.94 4.97 5.05 4.97 4.97 5.05 5.05 9.93 9.97 10.0 10.1 9.93 10.1 10.1 10.1

370.6 406.8 406.8 525.2 345.3 613.8 489.3 282.7 575.9 324.0 535.6 293.9 303.8 465.5 579.2 502.1 509.9 286.8 546.9 260.2 484.7 484.7 356.1 356.1 370.6 484.0 525.1 406.8 489.2 379.0 450.9 414.2

0.134 0.133 0.133 0.134 0.129 0.129 0.130 0.129 0.125 0.126 0.125 0.126 0.124 0.124 0.125 0.124 0.122 0.123 0.123 0.123 0.115 0.115 0.114 0.115 0.135 0.135 0.135 0.135 0.132 0.131 0.132 0.131

314.49 315.11 315.49 315.62 334.68 335.68 334.55 335.33 355.56 355.40 355.91 354.78 375.64 375.33 374.54 375.07 274.71 275.02 274.86 275.87 294.85 295.36 295.25 295.04 315.19 314.28 314.59 315.63 335.62 334.87 335.50 334.48

10.0 10.1 10.1 10.1 9.93 9.93 10.0 10.0 9.99 10.0 10.0 10.1 9.93 10.0 10.1 10.1 19.9 19.9 20.0 20.0 19.9 20.0 20.0 20.1 19.9 20.0 20.0 20.1 19.9 20.0 20.0 20.1

265.3 388.6 459.1 496.5 303.8 502.1 275.5 430.4 439.6 406.5 509.9 286.8 450.7 386.4 247.3 356.1 303.4 370.5 336.1 525.0 345.2 450.8 414.1 378.9 423.1 238.1 293.8 496.4 502.2 364.4 465.6 275.6

0.128 0.128 0.128 0.127 0.127 0.127 0.127 0.127 0.120 0.121 0.121 0.121 0.117 0.116 0.117 0.117 0.138 0.138 0.138 0.138 0.134 0.135 0.134 0.135 0.130 0.131 0.131 0.131 0.129 0.129 0.130 0.130

354.92 355.24 355.55 354.60 375.47 374.50 374.56 374.85 275.50 274.98 274.78 275.15 295.07 295.17 295.71 294.74 314.34 315.14 314.46 315.53 334.45 334.52 335.06 335.57 355.32 354.84 354.96 355.13 374.68 375.62 375.18 375.49

19.9 20.0 20.0 20.1 19.9 19.9 19.9 20.0 29.9 29.7 29.9 30.0 30.0 30.0 30.0 29.9 30.0 30.0 30.0 30.0 29.9 29.9 30.0 30.1 29.8 30.0 30.1 30.2 29.8 29.9 30.0 30.1

344.1 406.5 439.6 260.2 450.7 247.3 272.7 327.1 483.9 370.5 336.1 406.7 414.0 450.7 528.9 345.1 265.2 423.1 293.8 496.4 275.5 303.7 396.7 502.1 406.5 314.9 344.1 374.7 299.3 484.8 417.9 450.8

0.123 0.124 0.124 0.124 0.120 0.120 0.120 0.121 0.141 0.140 0.141 0.141 0.137 0.137 0.137 0.137 0.133 0.133 0.133 0.133 0.119 0.119 0.118 0.118 0.126 0.127 0.126 0.126 0.123 0.123 0.123 0.123

Table 4. Thermal Conductivity of Dimethoxymethane + Diesel Fuel; w ) 0.10 Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

276.09 274.97 275.93 275.00 295.30 294.70 295.66 294.91 315.25 316.02 315.66 314.87 334.98 335.48 336.05 335.20 355.86 354.66 355.18 354.32 374.82 374.82 375.30 375.69 275.86 276.10 274.98 275.35 295.31 295.14 295.10 294.83

5.01 5.05 5.05 4.97 4.97 5.03 5.05 5.09 5.05 5.05 5.05 5.09 4.97 4.97 5.01 5.01 5.05 5.05 4.97 4.97 4.88 4.92 4.92 4.97 10.0 10.0 10.0 10.0 10.0 10.0 10.0 9.93

567.3 335.8 524.5 335.8 414.4 282.9 451.1 313.3 479.8 598.9 543.5 394.2 385.9 456.0 542.4 492.1 556.3 386.0 484.7 310.4 299.6 299.6 386.8 451.2 542.7 601.3 350.2 445.4 414.5 379.3 379.3 313.4

0.136 0.135 0.135 0.135 0.131 0.131 0.130 0.131 0.127 0.127 0.126 0.127 0.123 0.123 0.123 0.123 0.119 0.119 0.119 0.119 0.116 0.115 0.115 0.115 0.136 0.136 0.135 0.136 0.132 0.132 0.132 0.132

316.25 315.87 314.79 315.35 334.68 335.27 336.13 335.85 356.02 355.86 355.37 354.76 375.26 374.90 375.86 376.23 275.07 275.06 275.03 274.97 294.60 295.20 295.83 295.62 315.27 316.01 314.54 315.85 336.01 335.87 335.22 334.48

10.0 10.0 10.0 10.1 9.93 9.93 9.93 10.0 9.97 10.0 10.0 10.1 10.0 10.0 10.0 10.1 20.1 20.1 20.1 20.1 20.0 20.0 20.0 20.2 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.1

640.2 566.4 339.6 464.0 352.2 473.6 621.4 567.9 618.3 588.3 483.0 340.4 413.2 338.4 528.6 612.1 370.2 370.2 370.2 370.2 282.9 414.5 529.5 489.6 465.4 609.4 312.5 566.4 615.3 576.4 445.7 305.7

0.128 0.128 0.128 0.128 0.125 0.125 0.125 0.125 0.121 0.121 0.122 0.121 0.117 0.118 0.118 0.118 0.139 0.139 0.140 0.139 0.135 0.135 0.135 0.135 0.131 0.131 0.132 0.131 0.128 0.128 0.128 0.128

355.20 355.62 354.52 356.04 376.21 375.77 375.46 374.54 274.91 275.16 275.83 276.01 295.14 294.70 295.00 295.75 314.82 315.28 315.88 315.53 335.29 336.15 335.93 335.57 355.65 356.04 354.91 355.12 375.93 375.58 375.30 374.79

20.0 20.0 20.0 20.1 20.0 20.0 20.0 20.0 30.0 30.0 29.9 29.9 30.0 30.0 30.0 30.0 30.0 30.0 30.1 30.1 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0

422.2 508.9 295.2 610.3 623.2 529.6 462.0 292.4 382.2 452.3 591.2 645.9 414.4 313.4 379.2 529.5 393.0 471.5 582.9 523.9 476.2 685.6 621.1 539.5 495.8 572.8 355.7 400.6 581.6 498.2 468.4 353.1

0.125 0.125 0.124 0.125 0.121 0.121 0.121 0.121 0.142 0.142 0.142 0.142 0.138 0.138 0.138 0.137 0.135 0.134 0.135 0.134 0.131 0.130 0.131 0.131 0.127 0.127 0.127 0.127 0.123 0.123 0.123 0.124

4 were fitted from the experimental data at different pressures and temperatures, respectively. Usually the thermal conductivity of fluids is correlated as the function of density and temperature. But the PVT data of dimethoxymethane have not been reported at present. In this paper, therefore, the experimental results of liquid dimethoxy-

methane were correlated by a polynomial of temperature and pressure: 1

λ/W‚m-1‚K-1 )

2

∑ ∑ a (T/K) (P/MPa) i

ij

i)0 j)0

j

(2)

Journal of Chemical and Engineering Data, Vol. 51, No. 5, 2006 1747 Table 5. Thermal Conductivity of Dimethoxymethane + Diesel Fuel; w ) 0.15' Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

Tr/K

P/MPa

q/mW‚m-1

λ/W‚m-1‚K-1

275.39 275.49 274.65 276.05 294.44 294.66 295.52 295.77 314.89 315.45 314.42 315.08 335.13 335.30 336.37 335.98 356.03 354.14 356.63 354.79 375.26 374.86 376.12 375.57 274.98 275.56 274.50 275.36 294.62 294.80 295.13 295.60

4.97 4.97 5.05 5.05 5.05 5.05 5.05 5.05 5.01 5.01 5.05 5.05 5.05 5.05 5.05 4.97 5.01 5.01 5.05 5.05 5.01 5.01 5.05 5.05 9.97 9.97 9.97 10.0 10.1 10.1 10.1 10.1

439.9 478.9 300.2 562.3 279.7 309.9 484.1 523.5 354.0 457.0 264.1 386.9 425.7 485.0 622.6 582.1 585.3 303.9 666.3 462.7 419.6 325.7 629.3 472.1 366.5 478.7 269.4 439.7 309.8 341.6 409.8 484.0

0.136 0.136 0.136 0.136 0.132 0.132 0.131 0.132 0.127 0.128 0.127 0.128 0.124 0.124 0.124 0.124 0.120 0.120 0.120 0.120 0.116 0.116 0.117 0.116 0.137 0.137 0.136 0.137 0.133 0.133 0.132 0.132

314.67 314.75 315.15 315.44 335.97 336.35 335.20 334.52 354.50 356.01 355.35 355.85 375.29 376.14 374.76 375.56 274.53 274.84 275.48 274.40 294.38 295.06 294.57 295.48 314.61 315.08 315.30 314.45 335.98 335.65 335.21 334.48

10.1 10.1 10.1 10.1 10.1 10.1 10.0 10.0 10.1 10.1 10.0 10.0 10.1 10.0 10.0 10.1 19.9 20.0 20.1 20.1 20.0 20.0 20.1 20.1 20.0 20.0 20.0 20.1 20.1 20.1 20.1 20.1

322.6 354.1 421.3 457.1 565.3 631.2 435.7 299.8 325.3 635.1 502.4 599.2 423.1 631.6 321.3 496.3 299.8 366.2 478.2 269.1 279.6 409.6 309.7 483.8 322.5 421.3 457.1 292.6 630.1 568.2 470.6 324.1

0.127 0.129 0.128 0.128 0.125 0.125 0.126 0.126 0.122 0.122 0.122 0.122 0.118 0.119 0.118 0.118 0.140 0.141 0.140 0.141 0.136 0.136 0.136 0.136 0.132 0.132 0.133 0.132 0.129 0.129 0.129 0.129

354.88 355.34 355.85 356.24 376.03 375.76 375.37 374.67 275.87 275.16 275.33 274.45 295.58 294.49 294.80 294.69 314.22 314.36 315.22 315.32 336.02 335.80 334.56 335.57 355.28 355.95 354.74 355.58 375.24 375.64 375.90 374.76

20.0 20.1 20.1 20.1 19.9 19.9 20.0 20.0 29.9 30.1 30.1 30.1 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.1

381.4 466.9 590.0 692.7 633.2 567.5 456.4 319.8 561.0 439.1 478.1 299.7 523.3 309.8 374.9 358.0 264.1 292.6 457.0 494.2 678.2 618.3 341.4 552.8 450.3 582.8 337.1 518.6 467.9 556.9 612.1 355.7

0.125 0.125 0.126 0.125 0.121 0.122 0.121 0.121 0.143 0.143 0.144 0.143 0.139 0.140 0.139 0.139 0.135 0.135 0.135 0.136 0.132 0.131 0.132 0.131 0.128 0.127 0.128 0.127 0.124 0.124 0.124 0.124

Table 6. Coefficients aIjk/W‚m-1‚K-(j+1)‚MPa-k Used in Equation 3 i)0 i)1

j)0 j)1 j)0 j)1

k)0

k)1

k)2

1.825 × 10-1 -1.888 × 10-4 6.372 × 10-2 -1.336 × 10-4

7.775 × 10-5 1.107 × 10-6 -5.247 × 10-3 1.412 × 10-5

5.880 × 10-8 -1.315 × 10-8 1.977 × 10-4 -5.407 × 10-7

The coefficients in eq 2 for dimethoxymethane are listed in Table 2. The correlation can represent the experimental data for liquid dimethoxymethane with the standard deviation of 0.41 % and the maximum deviation of 1.2 % as shown in Figure 5. To our knowledge, only our group has reported the thermal conductivity of dimethoxymethane at the saturation pressure with an uncertainty less than ( 2 %. Figure 6 illustrates our previous work and the present experimental data at the saturation pressure. Figure 7 shows the relative deviations between them. It can be learned that the deviations are in the declared uncertainty. Compared to our previous work, the measurement system was improved including more advance instruments and new data acquired rate speeded up from 17 readings to 50 readings per second. It can be concluded that the measured data in this paper are more convincing. Dimethoxymethane + Diesel Fuel. The measurements of the thermal conductivity of three mixtures of dimethoxymethane + diesel fuel were carried out in the temperature range from (275 to 375) K and in the pressure range from (5 to 30) MPa with dimethoxymethane mass fractions of 0.05, 0.10, and 0.15. The experimental results of the three mixtures are listed in Tables 3 to 5, respectively. For engineering applications, the experimental data were correlated by the following correlation: 1

λ/W‚m-1‚K-1 )

1

2

∑∑∑a i)0 j)0 k)0

i j k ijkw (T/K) (P/MPa)

(3)

Figure 8. Relative deviations of calculated values by eq 3 from experimental data for dimethoxymethane + diesel fuel: O, 0.05; g, 0.10; 4, 0.15.

where w is the mass fraction of dimethoxymethane, 0.05 e w e 0.15. The coefficients in eq 3 for dimethoxymethane are listed in Table 6. Figure 8 illustrates the deviations of the experimental values from eq 3. The maximum deviation is 0.92 %, and the standard deviation is 0.28 %.

Conclusion The thermal conductivity of liquid dimethoxymethane was measured in the temperature range form (245 to 385) K and pressure range from saturation pressure to 30 MPa. The correlation of the experimental data was provided with the maximum deviation of 1.2 % and the standard deviation of 0.41 %. The thermal conductivity of mixtures of dimethoxymethane + diesel fuel had been measured in the temperature range from (275 to 375) K and in the pressure range from (5 to 30) MPa.

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Journal of Chemical and Engineering Data, Vol. 51, No. 5, 2006

The experimental data were correlated as a function of temperature, pressure, and mass fraction with the maximum deviation of 0.92 % and the standard deviation of 0.28 %. The expanded uncertainty of the experimental data was estimated within ( 2.0 % with the coverage factor k ) 2.

Literature Cited (1) Ren, Y.; Huang, Z. H.; Jiang, D. M.; Liu, L. X. Study on combustion characteristics of a direct injection diesel engine operating on diesel/ dimethoxymethane blends. Trans. CSICE 2005, 23, 97-104. (2) Pan, J.; Wu, J. T.; Liu, Z. G.; Jin, X. G. Measurement of the thermal conductivity of liquid dimethoxymethane from 240 to362 K. Int. J. Thermophys. 2004, 25, 701-708. (3) Jin, X. G.; Wu, J. T.; Liu, Z. G.; Pan, J. The thermal conductivity of dimethyl carbonate in the liquid phase. Fluid Phase Equilib. 2004, 220, 37-40. (4) Wang, Y. G.; Wu, J. T.; Liu, Z. G. Thermal conductivity of gaseous dimethyl ether from (263 to 383) K. J. Chem. Eng. Data 2006, 51, 164-168. (5) Healy, J. J.; De Groot, J. J.; Kestin, J. The theory of the transient hot-wire method for measuring thermal conductivity. Physica C 1976, 82, 392-408.

(6) Wakeham, W. A.; Nagashima, A.; Sengers, J. V. Experimental Thermodynamics: Vol. III, Measurement of the Transport Properties of Fluids; Blackwell Scientific Publications: Oxford, 1991. (7) Wu, J. T. Development of the new thermophysical properties measurement system and research of thermophysical properties of dimethyl ether. Ph.D. Dissertation, Xi’an Jiaotong University, Xi’an, 2003. (8) Wu, J. T.; Liu, Z. G.; Pan, J.; Zhao, X. M. Vapor pressure measurements of dimethyl ether from (233 to 399) K. J. Chem. Eng. Data 2004, 49, 32-34. (9) Ramires, M. L. V.; Nieto de Casto, C. A.; Perkings, R. A.; Nagasaka, Y.; Assael, M. J.; Wakeham, W. A. Reference data for the thermal conductivity of saturated liquid toluene over a wide range of temperatures. J. Phys. Chem. Ref. Data 2000, 29, 133-139.

Received for review April 16, 2006. Accepted July 16, 2006. This research was supported by the National Basic Research Priorities Program of Ministry of Science and Technology of China (Grant 2001CB209208) and the National Natural Science Foundation of China (Grant 50336020).

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